diff --git a/death-clock-core.js b/death-clock-core.js
index 9ae989d..f27fea0 100644
--- a/death-clock-core.js
+++ b/death-clock-core.js
@@ -514,6 +514,80 @@ function sessionEquivalences(sessionTokens) {
   return list;
 }
 
+// ============================================================
+// ACCELERATOR GAME — Pure Helpers
+// ============================================================
+
+/**
+ * All possible session challenge definitions.
+ * Each entry: { id, icon, label, desc, type, target, rewardDp }
+ * type: 'taps' | 'tokens' | 'combo' | 'speed' | 'upgrade' | 'co2'
+ */
+const SESSION_CHALLENGE_DEFS = [
+  { id: 'rapid_fire',    icon: '👆', label: 'Rapid Fire',         desc: 'Tap 100 times',                                      type: 'taps',    target: 100,   rewardDp: 200  },
+  { id: 'billionaire',   icon: '💎', label: 'Token Billionaire',  desc: 'Contribute 1 billion personal tokens',               type: 'tokens',  target: 1e9,   rewardDp: 100  },
+  { id: 'trillion',      icon: '💰', label: 'Trillion Touched',   desc: 'Contribute 1 trillion personal tokens',              type: 'tokens',  target: 1e12,  rewardDp: 1000 },
+  { id: 'combo_king',    icon: '🔥', label: 'Combo King',         desc: 'Hit 10× combo 3 times',                              type: 'combo',   target: 3,     rewardDp: 500  },
+  { id: 'speed_demon',   icon: '⚡', label: 'Speed Demon',        desc: 'Tap 50 times in under 10 seconds',                   type: 'speed',   target: 50,    rewardDp: 500  },
+  { id: 'first_upgrade', icon: '🛒', label: 'Consumer Capitalism',desc: 'Purchase your first upgrade',                        type: 'upgrade', target: 1,     rewardDp: 50   },
+  { id: 'carbon_sprint', icon: '💨', label: 'Carbon Sprint',      desc: 'Generate 1 tonne CO₂-equivalent in one session',    type: 'co2',     target: 1000,  rewardDp: 750  },
+];
+
+/**
+ * Return the first personal milestone that the player has not yet crossed.
+ * @param {number} personalTokens
+ * @param {Array}  milestones
+ * @returns {Object|null}
+ */
+function getNextMilestoneForPlayer(personalTokens, milestones) {
+  if (typeof personalTokens !== 'number' || !Array.isArray(milestones)) return null;
+  return milestones.find((m) => personalTokens < m.tokens) || null;
+}
+
+/**
+ * Calculate the combo multiplier based on recent tap timestamps.
+ * Counts taps within the last 1,000 ms of the most recent tap, capped at 10.
+ * @param {number[]} tapTimestamps - array of epoch-ms tap times (oldest first)
+ * @returns {number} integer 1–10
+ */
+function computeComboMultiplier(tapTimestamps) {
+  if (!Array.isArray(tapTimestamps) || tapTimestamps.length === 0) return 1;
+  const latest = tapTimestamps[tapTimestamps.length - 1];
+  if (typeof latest !== 'number' || !isFinite(latest)) return 1;
+  const cutoff = latest - 1000;
+  const recent = tapTimestamps.filter((t) => typeof t === 'number' && t >= cutoff);
+  return Math.min(10, Math.max(1, recent.length));
+}
+
+/**
+ * Return 3 session challenges selected deterministically from SESSION_CHALLENGE_DEFS
+ * using a daily seed (changes once per UTC day).
+ * @param {number} [seedMs] - seed timestamp in ms (defaults to Date.now())
+ * @returns {Array<Object>} exactly 3 challenge definition objects
+ */
+function getSessionChallenges(seedMs) {
+  const ts = typeof seedMs === 'number' && isFinite(seedMs) ? seedMs : Date.now();
+  const dayBucket = Math.abs(Math.floor(ts / 86400000));
+  const start = dayBucket % SESSION_CHALLENGE_DEFS.length;
+  const result = [];
+  for (let i = 0; i < 3; i++) {
+    result.push(SESSION_CHALLENGE_DEFS[(start + i) % SESSION_CHALLENGE_DEFS.length]);
+  }
+  return result;
+}
+
+/**
+ * Format a Doom Points value into a human-readable string.
+ * @param {number} dp
+ * @returns {string}
+ */
+function formatDoomPoints(dp) {
+  if (typeof dp !== 'number' || isNaN(dp) || dp < 0) return '0 DP';
+  if (dp >= 1e6) return (dp / 1e6).toFixed(1).replace(/\.0$/, '') + 'M DP';
+  if (dp >= 1e3) return (dp / 1e3).toFixed(1).replace(/\.0$/, '') + 'K DP';
+  return Math.round(dp) + ' DP';
+}
+
 // ============================================================
 // EXPORTS — CommonJS for Jest; window global for the browser
 // ============================================================
@@ -524,6 +598,7 @@ const DeathClockCore = {
   HISTORICAL_DATA,
   MILESTONES,
   RATE_SCHEDULE,
+  SESSION_CHALLENGE_DEFS,
   TOKEN_TIPS,
   formatTokenCount,
   formatTokenCountShort,
@@ -540,6 +615,10 @@ const DeathClockCore = {
   generateEquivalences,
   calculatePersonalFootprint,
   sessionEquivalences,
+  getNextMilestoneForPlayer,
+  computeComboMultiplier,
+  getSessionChallenges,
+  formatDoomPoints,
 };
 
 if (typeof module !== 'undefined' && module.exports) {
diff --git a/docs/prd/prd-accelerate-the-doom.md b/docs/prd/prd-accelerate-the-doom.md
new file mode 100644
index 0000000..8f8018c
--- /dev/null
+++ b/docs/prd/prd-accelerate-the-doom.md
@@ -0,0 +1,260 @@
+# PRD: Accelerate the Doom 🚀💀
+
+## Overview
+
+Turn passive dread into active participation. Give visitors a one-tap "Feed the Machine" clicker
+mechanic where every tap represents them personally contributing tokens to the global AI inference
+flood. The darker irony: you *know* it's bad and you keep tapping anyway. Built to be fast,
+frictionless, and finger-friendly on mobile.
+
+---
+
+## Problem
+
+The site currently shows what AI is doing *to* the world, but the visitor is a bystander. Adding
+an interactive clicker that lets visitors voluntarily accelerate the countdown makes the
+complicity visceral — and makes the site dramatically more fun and shareable. Cookie Clicker
+proved that people will enthusiastically click a button to destroy things if the numbers go up.
+
+---
+
+## Goals
+
+- Give visitors a direct, tactile way to interact with the token counter
+- Surface the dark irony: the visitor is choosing to accelerate environmental milestones
+- Make the experience finger-friendly on mobile (large tap targets, haptic-style feedback)
+- Integrate with the existing Doom Achievements badge system
+- Keep the feature entirely client-side with no new runtime dependencies
+
+---
+
+## Non-Goals
+
+- Modifying the real global counter — the clicker runs a separate "personal acceleration" track
+- Persistent server-side leaderboards (localStorage best-score only, v2 for cloud board)
+- Complex idle-game mechanics (cookie clicker auto-generators, prestige resets — v2)
+- Actual AI inference (the tokens are fictional within the game layer)
+
+---
+
+## Feature Description
+
+### Core Mechanic — "Feed the Machine" 🤖
+
+A new collapsible section **(or modal, TBD in design)** titled **"🚀 Accelerate the Doom"** contains
+a large circular tap target — the **Big Red Button** — styled as a glowing reactor core or CPU chip.
+
+Every tap/click:
+1. Adds tokens to a **personal acceleration counter** (`personalTokens`)
+2. Applies a **tap multiplier** (starts at 1×, upgrades increase it)
+3. Triggers a brief CSS pulse animation on the button (visual feedback)
+4. On mobile: fires a `navigator.vibrate(30)` haptic pulse (gracefully ignored if unsupported)
+5. Increments a **Tap Combo** counter — rapid taps within 1 second build a combo multiplier up
+   to 10× (combo resets if the user pauses > 1.5 s)
+
+The button label changes with the combo level:
+- 1× — "Feed the Machine"
+- 2×–4× — "Keep Going…"
+- 5×–9× — "FASTER! 🔥"
+- 10× — "MAXIMUM DOOM ☢️"
+
+### Personal Acceleration Counter
+
+A stats strip below the button shows the player's running personal total:
+
+```
+🤖 You've personally contributed:
+   1,240,000 tokens  (≈ 0.0004 kWh · 0.17 g CO₂ · 0.62 mL water)
+   Tap rate: 3.2/sec
+```
+
+These stats reuse `calculateEnvironmentalImpact()` from `death-clock-core.js`.
+
+### Upgrade Shop 🛒
+
+Earn **Doom Points** (DP) equal to tokens contributed ÷ 1,000. Spend DP to buy
+one-time multiplier upgrades, displayed as a mini "shop" of unlockable cards:
+
+| Upgrade | Cost (DP) | Effect | Flavour Text |
+|---------|-----------|--------|--------------|
+| 🖥️ Extra GPU Rack | 10 | 2× tokens per tap | "More cores, more chaos" |
+| ⚡ Liquid Cooling Override | 50 | 5× tokens per tap | "Ignore the thermal warnings" |
+| 🌍 Global Data Centre | 200 | 10× tokens per tap | "Every continent contributing" |
+| 🛰️ Orbital Inference Array | 1,000 | 25× tokens per tap | "Space itself regrets this" |
+| 🧬 AGI Mode | 5,000 | 100× tokens per tap | "It's writing its own prompts now" |
+
+Upgrades are stored in `localStorage` key `tokenDeathclockUpgrades` (JSON object of upgrade IDs
+→ boolean). Shop cards use a disabled/greyed state when unaffordable.
+
+### Milestone Racing 🏁
+
+The section header shows a **"Next milestone you could trigger"** target — the next upcoming
+environmental milestone that the player's personal counter is approaching. A progress bar fills
+as `personalTokens` approaches that threshold.
+
+When the player's personal counter crosses a milestone threshold:
+- The milestone card in the Milestones section flashes with a special **"Accelerated by You"**
+  red pulse border for 5 seconds
+- A distinct achievement toast fires: *"🚀 You personally triggered [Milestone Name]! Catastrophe achieved."*
+- A new milestone-accelerator badge is earned (see Achievements integration below)
+
+Milestones are ordered ascending by `tokens` from the existing `MILESTONES` array in `death-clock-core.js`.
+The player's first reachable milestone is the one with the smallest `tokens` value greater than
+`personalTokens`.
+
+### Challenges ⚡
+
+Three rotating daily/session challenges (seeded by `Date.now()` divided into 24-hour buckets)
+give the player short-term goals. Examples:
+
+| Challenge | Goal | Reward |
+|-----------|------|--------|
+| Speed Demon | Reach 10 tap/sec for 3 consecutive seconds | 2× DP bonus for 60 s |
+| Trillion Touched | Contribute 1 trillion personal tokens | Unlock "Trillion Villain" badge |
+| Combo King | Hit 10× combo 3 times | +500 DP bonus |
+| Carbon Sprint | Generate 1 kg CO₂-equivalent in under 60 seconds | Special toast |
+| Nocturnal Accelerator | Complete any challenge between 00:00–04:00 local time | Easter-egg badge |
+
+Challenges are rendered as a horizontal scrollable row of cards on mobile, visible above the
+upgrade shop. A completed challenge card shows a green ✔ checkmark. Challenges reset per session
+(no localStorage persistence, keeping the UX frictionless).
+
+### Best Score / Hall of Shame
+
+A single row below the button shows:
+```
+🏆 Your best session:  42,000,000,000 tokens   (vs. today: 1,240,000)
+```
+
+Stored in `localStorage` key `tokenDeathclockBestScore`. Resets if the user clears localStorage.
+A subtle **"😱 New Record!"** pulse animation triggers when the current session beats the stored best.
+
+---
+
+## Mobile UX Requirements
+
+| Requirement | Detail |
+|-------------|--------|
+| **Touch target size** | Big Red Button minimum 96 × 96 px (WCAG 2.5.5 Target Size) |
+| **Tap responsiveness** | CSS `:active` state responds within 16 ms (no `touchstart` delay) |
+| **Haptic feedback** | `navigator.vibrate(30)` on each tap; 80ms on milestone trigger |
+| **No hover-only affordances** | All tooltips/shop descriptions accessible via tap-to-expand |
+| **Combo counter** | Positioned above button, large font — readable at arm's length |
+| **Horizontal challenge row** | `-webkit-overflow-scrolling: touch` + `scroll-snap` for snap-card UX |
+| **Upgrade shop** | 2-column grid on mobile (<480 px), 3–4 columns on desktop |
+| **No layout shift** | Section collapses/expands with `max-height` transition, not `hidden` toggle |
+
+---
+
+## New Doom Achievements (extend existing badge system)
+
+The following badges integrate with the existing `tokenDeathclockBadges` localStorage key:
+
+| Badge | Name | Condition |
+|-------|------|-----------|
+| 🚀 | Accelerant | First tap on the Big Red Button |
+| 🔥 | Arsonist | Reach 10× combo for the first time |
+| ⚡ | Trillion Villain | Personally contribute 1 trillion tokens |
+| 🌍 | Continental Threat | Purchase the Global Data Centre upgrade |
+| 🛰️ | Space Criminal | Purchase the Orbital Inference Array upgrade |
+| 🧬 | Godlike | Purchase the AGI Mode upgrade |
+| 🏁 | First Blood | Personally trigger your first milestone |
+| ☠️ | Apex Accelerant | Personally trigger 5 milestones |
+| 🌙 | Nocturnal Accelerator | Complete a challenge between 00:00–04:00 |
+| 📤 | Bragging Rights | Share your personal acceleration total |
+
+---
+
+## Shareable Outcome
+
+A **"📤 Share My Destruction"** button (shown once `personalTokens > 0`) generates:
+
+> 🚀 I personally accelerated AI's environmental doom by contributing **1.24 billion tokens**
+> in one sitting. That's **0.37 g of CO₂**, **0.62 mL of water**, and one step closer to
+> [Next Milestone Name]. Come join me in accelerating the apocalypse.
+> → [link] #AccelerateTheDoom #TokenDeathClock
+
+Share flow reuses the existing `renderSharePanel()` / Twitter-X deep-link pattern already
+established in `script.js`.
+
+---
+
+## Implementation Notes
+
+### Pure Functions (death-clock-core.js)
+
+- `calculatePersonalImpact(personalTokens, tapMultiplier)` → `{ tokens, kWh, co2Kg, waterL }` — thin wrapper around existing `calculateEnvironmentalImpact()`
+- `getNextMilestoneForPlayer(personalTokens, milestones)` → milestone object or `null`
+- `computeComboMultiplier(tapTimestamps)` → integer 1–10 (input: array of recent tap epoch-ms values)
+- `getSessionChallenge(seedMs)` → array of 3 challenge objects `{ id, label, goal, rewardDesc }`
+- `formatDoomPoints(dp)` → string (e.g. `"1,240 DP"`)
+
+### DOM / Script (script.js)
+
+- `initAcceleratorSection()` — sets up button listeners, combo timer, RAF-driven stat strip updates
+- `handleTap()` — called on `pointerdown` (covers mouse + touch in one event); updates `personalTokens`, combo state, DP balance, checks challenges and milestone crossings
+- `renderUpgradeShop()` — renders upgrade cards, wires purchase buttons, reads/writes `localStorage`
+- `checkAcceleratorAchievements()` — called from `handleTap()` and on milestone cross; delegates to existing badge unlock flow
+- Combo timer: `setInterval` at 100 ms checking last-tap timestamp to reset combo
+
+### HTML (index.html)
+
+New `<section id="accelerator-section">` inserted between `#achievements-section` and `<footer>`.
+Contains:
+- `.accelerator-header` (`<h2>`, description text)
+- `#bigRedButton` (`<button>` with `aria-label`, large CSS-styled tap zone)
+- `#comboDisplay` (combo multiplier indicator)
+- `#personalStatsStrip` (tokens / kWh / CO₂ / water)
+- `#milestoneRaceBar` (next milestone progress bar)
+- `#challengeRow` (horizontal scroll container)
+- `#upgradeShop` (upgrade card grid)
+- `#bestScoreRow`
+- `#shareAccelerationBtn`
+
+### CSS (styles.css)
+
+- `.big-red-button` — large circular button, `box-shadow` pulsing animation on `:active`
+- `.big-red-button.combo-max` — extra glow class applied at 10× combo
+- `.upgrade-card` — grid card with `opacity: 0.4` + `pointer-events: none` when unaffordable
+- `.challenge-card` — horizontal scroll snap card, `.completed` variant with ✔ overlay
+- `.milestone-race-bar` — CSS `transition: width` progress bar
+- All new colours pull from existing CSS custom properties (`--accent`, `--text-dim`, etc.)
+
+### No New Runtime Dependencies
+
+Everything runs in vanilla JS + existing Chart.js CDN. `navigator.vibrate()` is optional/graceful.
+No canvas screenshot library, no game engine, no animation library.
+
+---
+
+## Accessibility
+
+| Concern | Approach |
+|---------|----------|
+| Button label | `aria-label` updates with current combo: *"Feed the Machine — 3× combo"* |
+| Combo display | `aria-live="polite"` region announces combo changes at natural reading speed |
+| Upgrade shop | Each card is a `<button>` with descriptive `aria-label`; disabled cards carry `aria-disabled="true"` |
+| Progress bar | `role="progressbar"` with `aria-valuenow`, `aria-valuemin`, `aria-valuemax` |
+| Challenges | `role="list"` + `role="listitem"` on challenge row |
+| Haptics | Never the sole indicator of an event — all haptic moments have visual counterparts |
+| Reduced motion | All pulse/shake animations wrapped in `@media (prefers-reduced-motion: no-preference)` |
+
+---
+
+## Success Metrics
+
+- Average session duration increases (accelerator gives a reason to stay)
+- Return visit rate increases (upgrades persist in localStorage — the shop is always there)
+- Social shares containing personal token count or milestone trigger message
+- Badge earn rate for accelerator-specific badges
+
+---
+
+## Open Questions
+
+- Should the Big Red Button have a "cool-down" between taps to encourage rhythm over mashing? (Might be more fun with no cap — test both)
+- Should we add an **Auto-Clicker** upgrade (idle-game style) that generates tokens while you're away? (Strong v2 feature — keep v1 manual-only to preserve intentionality of "you're choosing to do this")
+- Should `personalTokens` persist across sessions in `localStorage`? (Would make the progression feel more meaningful — risk: the upgrade shop becomes trivially unlocked quickly; consider resetting DP but not upgrading the multipliers)
+- Should the section be fully open by default on first visit, or collapsed like the calculator? (Mobile first-visit UX — probably collapsed but with a teaser animation)
+- Leaderboard via GitHub Issues / Gist API for a lightweight social scoreboard? (Fun v2 experiment — adds server interaction, out of scope for v1)
+- Should milestone triggers from the player's personal counter be visually distinguished from the global counter crossing milestones? (Yes — different border colour and badge labelling)
diff --git a/index.html b/index.html
index e5877fd..c5184d2 100644
--- a/index.html
+++ b/index.html
@@ -293,6 +293,83 @@ <h2>🏆 Your Doom Badges</h2>
   </div>
 </section>
 
+<!-- ── Accelerate the Doom ──────────────────────────────── -->
+<section id="accelerator-section">
+  <div class="container">
+    <p class="section-label">&#x25A0; Gamification</p>
+    <h2>🚀 Accelerate the Doom</h2>
+    <p class="lb-desc">You know it's bad. Tap anyway. Every click adds tokens to your personal contribution to the apocalypse. Earn Doom Points, unlock upgrades, and trigger environmental milestones yourself.</p>
+    <button id="accelToggleBtn" class="scoring-toggle-btn" aria-expanded="false" aria-controls="accel-content">
+      ▶ Open Doom Accelerator
+    </button>
+    <div id="accel-content" hidden>
+
+      <!-- Personal stats strip -->
+      <div class="accel-stats-strip" aria-label="Personal acceleration stats">
+        <div class="accel-stat">
+          <div class="accel-stat-value" id="accelTokens">0</div>
+          <div class="accel-stat-label">Personal Tokens</div>
+        </div>
+        <div class="accel-stat">
+          <div class="accel-stat-value" id="accelCo2">0 g</div>
+          <div class="accel-stat-label">CO₂ Generated</div>
+        </div>
+        <div class="accel-stat">
+          <div class="accel-stat-value" id="accelWater">0 mL</div>
+          <div class="accel-stat-label">Water Used</div>
+        </div>
+        <div class="accel-stat accel-stat-dp">
+          <div class="accel-stat-value" id="accelDp">0 DP</div>
+          <div class="accel-stat-label">Doom Points</div>
+        </div>
+      </div>
+
+      <!-- Big Red Button area -->
+      <div class="brb-wrap">
+        <div id="comboDisplay" class="combo-display" aria-live="polite" aria-atomic="true" aria-label="Combo multiplier: 1×">1×</div>
+        <button id="bigRedButton" class="big-red-button" aria-label="Feed the Machine — 1× combo">
+          <span class="brb-icon" aria-hidden="true">⚙️</span>
+          <span id="brbLabel" class="brb-label">Feed the Machine</span>
+        </button>
+        <div class="brb-rate" id="brbTapRate">Tap to begin</div>
+      </div>
+
+      <!-- Milestone race bar -->
+      <div class="milestone-race-wrap">
+        <div class="milestone-race-header">
+          <span class="milestone-race-label">Next milestone: <strong id="milestoneRaceName">—</strong></span>
+          <span class="milestone-race-pct" id="milestoneRacePct">0%</span>
+        </div>
+        <div class="progress-bar" role="progressbar"
+             aria-label="Personal progress toward next milestone"
+             aria-valuenow="0" aria-valuemin="0" aria-valuemax="100"
+             id="milestoneRaceBar">
+          <div class="progress-fill milestone-race-fill" id="milestoneRaceFill" style="width:0%"></div>
+        </div>
+      </div>
+
+      <!-- Session Challenges -->
+      <div class="accel-section-title">⚡ Session Challenges</div>
+      <div id="challengeRow" class="challenge-row" role="list" aria-label="Session challenges">
+        <!-- populated by script.js -->
+      </div>
+
+      <!-- Upgrade Shop -->
+      <div class="accel-section-title">🛒 Upgrade Shop</div>
+      <div id="upgradeShop" class="upgrade-shop" aria-label="Upgrade shop">
+        <!-- populated by script.js -->
+      </div>
+
+      <!-- Footer row: best score + share -->
+      <div class="accel-footer-row">
+        <div id="bestScoreRow" class="best-score-row">🏆 Best session: <span id="bestScoreValue">—</span></div>
+        <button id="shareAccelerationBtn" class="btn-secondary" hidden>📤 Share My Destruction</button>
+      </div>
+
+    </div>
+  </div>
+</section>
+
 <!-- ── Footer ─────────────────────────────────────────────── -->
 <footer>
   <div class="container">
diff --git a/script.js b/script.js
index 5bd4817..849bc94 100644
--- a/script.js
+++ b/script.js
@@ -15,6 +15,7 @@
     HISTORICAL_DATA,
     MILESTONES,
     RATE_SCHEDULE,
+    SESSION_CHALLENGE_DEFS,
     TOKEN_TIPS,
     formatTokenCount,
     formatTokenCountShort,
@@ -31,6 +32,10 @@
     generateEquivalences,
     calculatePersonalFootprint,
     sessionEquivalences,
+    getNextMilestoneForPlayer,
+    computeComboMultiplier,
+    getSessionChallenges,
+    formatDoomPoints,
   } = window.DeathClockCore;
 
   // ---- State -----------------------------------------------
@@ -1263,6 +1268,16 @@
     { id: 'optimist',             icon: '\uD83C\uDF1E', name: 'Optimist',                 desc: 'Switched to Light Mode. Your optimism is noted.',    type: 'manual' },
     { id: 'nocturnal_doomer',     icon: '\uD83C\uDF13', name: 'Nocturnal Doomer',         desc: "Visiting between midnight and 4am. Can't sleep?",   type: 'easter' },
     { id: 'return_visitor',       icon: '\uD83D\uDD01', name: 'Glutton for Punishment',   desc: 'You came back. You knew what would happen.',         type: 'easter' },
+    // Accelerator badges
+    { id: 'accelerant',           icon: '\uD83D\uDE80', name: 'Accelerant',               desc: 'Made your first tap on the Big Red Button.',         type: 'manual' },
+    { id: 'arsonist',             icon: '\uD83D\uDD25', name: 'Arsonist',                 desc: 'Reached 10\xD7 combo for the first time.',           type: 'manual' },
+    { id: 'trillion_villain',     icon: '\u26A1',       name: 'Trillion Villain',         desc: 'Personally contributed 1 trillion tokens.',          type: 'manual' },
+    { id: 'continental_threat',   icon: '\uD83C\uDF0D', name: 'Continental Threat',       desc: 'Purchased the Global Data Centre upgrade.',          type: 'manual' },
+    { id: 'space_criminal',       icon: '\uD83D\uDEF0\uFE0F', name: 'Space Criminal',    desc: 'Purchased the Orbital Inference Array.',             type: 'manual' },
+    { id: 'godlike',              icon: '\uD83E\uDDEC', name: 'Godlike',                  desc: 'Purchased the AGI Mode upgrade.',                    type: 'manual' },
+    { id: 'first_blood',          icon: '\uD83C\uDFC1', name: 'First Blood',              desc: 'Personally triggered your first milestone.',         type: 'manual' },
+    { id: 'apex_accelerant',      icon: '\u2620\uFE0F', name: 'Apex Accelerant',         desc: 'Personally triggered 5 milestones.',                 type: 'manual' },
+    { id: 'bragging_rights',      icon: '\uD83D\uDCE4', name: 'Bragging Rights',          desc: 'Shared your personal acceleration total.',           type: 'manual' },
   ];
 
   const LS_BADGES_KEY = 'tokenDeathclockBadges';
@@ -1395,6 +1410,525 @@
     if (closeBtn) closeBtn.addEventListener('click', dismissToast);
   }
 
+  // ============================================================
+  // ACCELERATE THE DOOM
+  // ============================================================
+
+  // ---- Constants -------------------------------------------
+
+  /** Base tokens added to personal counter per tap (before multipliers). */
+  const ACC_BASE_TOKENS_PER_TAP = 1_000_000;
+
+  /** Doom Points earned per token (1 DP per 1 million tokens). */
+  const ACC_DP_PER_TOKEN = 1 / 1_000_000;
+
+  const UPGRADES = [
+    { id: 'gpu_rack',    icon: '\uD83D\uDDA5\uFE0F', name: 'Extra GPU Rack',          cost:    10, multiplier:   2, flavour: 'More cores, more chaos'               },
+    { id: 'liquid_cool', icon: '\u26A1',              name: 'Liquid Cooling Override', cost:    50, multiplier:   5, flavour: 'Ignore the thermal warnings'           },
+    { id: 'global_dc',   icon: '\uD83C\uDF0D',        name: 'Global Data Centre',      cost:   200, multiplier:  10, flavour: 'Every continent contributing'          },
+    { id: 'orbital',     icon: '\uD83D\uDEF0\uFE0F',  name: 'Orbital Inference Array', cost:  1000, multiplier:  25, flavour: 'Space itself regrets this'             },
+    { id: 'agi_mode',    icon: '\uD83E\uDDEC',        name: 'AGI Mode',                cost:  5000, multiplier: 100, flavour: "It's writing its own prompts now"      },
+  ];
+
+  const LS_UPGRADES_KEY   = 'tokenDeathclockUpgrades';
+  const LS_BESTSCORE_KEY  = 'tokenDeathclockBestScore';
+
+  // ---- State -----------------------------------------------
+
+  const acc = {
+    personalTokens:      0,
+    doomPoints:          0,
+    tapMultiplier:       1,
+    combo:               1,
+    tapTimestamps:       [],   // epoch-ms of recent taps (trimmed to last 3 s)
+    totalTaps:           0,
+    comboMaxHits:        0,    // times 10× combo was reached this session
+    milestonesTriggered: 0,    // personal milestones crossed this session
+    personalMilestoneSet: new Set(), // ids of milestones the player has crossed
+    bestScore:           0,
+    ownedUpgrades:       {},   // upgrade id → true
+    challenges:          [],   // active challenge defs (3)
+    challengeProgress:   {},   // challenge id → { value, completed }
+    sessionStartTokens:  0,    // snapshot of personalTokens when section opens (for carbon sprint)
+    sessionStartTime:    0,    // ms when section was opened
+    _comboResetTimer:    null,
+    _speedSecond:        { taps: 0, ts: 0 },  // taps in current 1-second bucket
+    _speedStreak:        0,    // consecutive 1-sec buckets with ≥ 10 taps
+  };
+
+  // ---- Persistence -----------------------------------------
+
+  function loadAcceleratorState() {
+    try {
+      const raw = localStorage.getItem(LS_UPGRADES_KEY);
+      if (raw) {
+        const parsed = JSON.parse(raw);
+        if (parsed && typeof parsed === 'object') acc.ownedUpgrades = parsed;
+      }
+    } catch (_) { /* ignore */ }
+    try {
+      const bs = parseFloat(localStorage.getItem(LS_BESTSCORE_KEY) || '0');
+      if (isFinite(bs) && bs > 0) acc.bestScore = bs;
+    } catch (_) { /* ignore */ }
+    // Recompute tap multiplier from owned upgrades
+    acc.tapMultiplier = currentTapMultiplier();
+  }
+
+  function saveAcceleratorState() {
+    try { localStorage.setItem(LS_UPGRADES_KEY, JSON.stringify(acc.ownedUpgrades)); } catch (_) { /* ignore */ }
+    try { localStorage.setItem(LS_BESTSCORE_KEY, String(acc.bestScore)); } catch (_) { /* ignore */ }
+  }
+
+  function currentTapMultiplier() {
+    let mult = 1;
+    UPGRADES.forEach((u) => {
+      if (acc.ownedUpgrades[u.id]) mult = Math.max(mult, u.multiplier);
+    });
+    return mult;
+  }
+
+  // ---- Tap handler -----------------------------------------
+
+  function handleTap() {
+    const now = Date.now();
+
+    // Record tap timestamp, keep a 3-second window
+    acc.tapTimestamps.push(now);
+    if (acc.tapTimestamps.length > 200) {
+      acc.tapTimestamps = acc.tapTimestamps.filter((t) => t >= now - 3000);
+    }
+
+    // Update combo
+    const newCombo = computeComboMultiplier(acc.tapTimestamps);
+    const hitMaxCombo = newCombo === 10 && acc.combo < 10;
+    acc.combo = newCombo;
+
+    // Tokens this tap
+    const tokensThisTap = ACC_BASE_TOKENS_PER_TAP * acc.tapMultiplier * acc.combo;
+    acc.personalTokens += tokensThisTap;
+    acc.doomPoints     += tokensThisTap * ACC_DP_PER_TOKEN;
+    acc.totalTaps++;
+
+    // Speed challenge tracking: bucket by 1-second windows
+    const secBucket = Math.floor(now / 1000);
+    if (secBucket === acc._speedSecond.ts) {
+      acc._speedSecond.taps++;
+    } else {
+      if (acc._speedSecond.taps >= 10) {
+        acc._speedStreak++;
+      } else {
+        acc._speedStreak = 0;
+      }
+      acc._speedSecond = { taps: 1, ts: secBucket };
+    }
+
+    // Combo-max hits (for combo_king challenge)
+    if (hitMaxCombo) acc.comboMaxHits++;
+
+    // Haptic
+    if (typeof navigator.vibrate === 'function') navigator.vibrate(30);
+
+    // Visual tap animation
+    const btn = document.getElementById('bigRedButton');
+    if (btn) {
+      btn.classList.add('tapping');
+      setTimeout(() => btn.classList.remove('tapping'), 140);
+    }
+
+    updateAcceleratorUI();
+    checkAcceleratorAchievements();
+    updateChallengeProgress();
+  }
+
+  // ---- Challenge progress ----------------------------------
+
+  function initChallengeProgress() {
+    acc.challenges = getSessionChallenges(Date.now());
+    acc.challengeProgress = {};
+    acc.challenges.forEach((c) => {
+      acc.challengeProgress[c.id] = { value: 0, completed: false };
+    });
+    acc.sessionStartTokens = acc.personalTokens;
+    acc.sessionStartTime   = Date.now();
+  }
+
+  function updateChallengeProgress() {
+    let anyChanged = false;
+    acc.challenges.forEach((c) => {
+      const p = acc.challengeProgress[c.id];
+      if (!p || p.completed) return;
+      let newValue = p.value;
+
+      switch (c.type) {
+        case 'taps':    newValue = acc.totalTaps; break;
+        case 'tokens':  newValue = acc.personalTokens; break;
+        case 'combo':   newValue = acc.comboMaxHits; break;
+        case 'upgrade': newValue = Object.keys(acc.ownedUpgrades).length; break;
+        case 'co2': {
+          const impact = calculateEnvironmentalImpact(acc.personalTokens);
+          newValue = impact.co2Kg; // target is in kg (1000 kg = 1 tonne)
+          break;
+        }
+        case 'speed': {
+          // Speed: 50 taps in under 10 seconds
+          // Check if the last 50 taps were within 10 seconds
+          if (acc.tapTimestamps.length >= 50) {
+            const earliest = acc.tapTimestamps[acc.tapTimestamps.length - 50];
+            const latest   = acc.tapTimestamps[acc.tapTimestamps.length - 1];
+            if (latest - earliest < 10000) {
+              newValue = c.target; // mark complete
+            }
+          }
+          break;
+        }
+        default: break;
+      }
+
+      if (newValue !== p.value) {
+        p.value = newValue;
+        anyChanged = true;
+        if (newValue >= c.target && !p.completed) {
+          p.completed = true;
+          p.value = c.target;
+          acc.doomPoints += c.rewardDp;
+          showChallengeComplete(c);
+          // Nocturnal bonus: any challenge completed between midnight and 4am
+          const hour = new Date().getHours();
+          if (hour >= 0 && hour < 4) awardBadge('nocturnal_doomer');
+        }
+      }
+    });
+    if (anyChanged) renderChallenges();
+  }
+
+  function showChallengeComplete(c) {
+    queueToast({
+      icon: c.icon,
+      name: 'Challenge Complete: ' + c.label,
+      desc: '+' + c.rewardDp + ' DP — ' + c.desc,
+    });
+  }
+
+  // ---- Achievements ----------------------------------------
+
+  function checkAcceleratorAchievements() {
+    if (acc.totalTaps === 1)                         awardBadge('accelerant');
+    if (acc.combo === 10)                            awardBadge('arsonist');
+    if (acc.personalTokens >= 1e12)                  awardBadge('trillion_villain');
+    if (acc.ownedUpgrades['global_dc'])              awardBadge('continental_threat');
+    if (acc.ownedUpgrades['orbital'])                awardBadge('space_criminal');
+    if (acc.ownedUpgrades['agi_mode'])               awardBadge('godlike');
+    if (acc.milestonesTriggered >= 1)                awardBadge('first_blood');
+    if (acc.milestonesTriggered >= 5)                awardBadge('apex_accelerant');
+  }
+
+  // ---- Upgrade purchase ------------------------------------
+
+  function purchaseUpgrade(id) {
+    const upgrade = UPGRADES.find((u) => u.id === id);
+    if (!upgrade || acc.ownedUpgrades[id]) return;
+    if (acc.doomPoints < upgrade.cost) return;
+    acc.doomPoints -= upgrade.cost;
+    acc.ownedUpgrades[id] = true;
+    acc.tapMultiplier = currentTapMultiplier();
+    saveAcceleratorState();
+
+    queueToast({
+      icon: upgrade.icon,
+      name: 'Upgrade Unlocked: ' + upgrade.name,
+      desc: upgrade.flavour + ' — now ' + upgrade.multiplier + '\xD7 per tap',
+    });
+
+    updateAcceleratorUI();
+    renderUpgradeShop();
+    checkAcceleratorAchievements();
+    updateChallengeProgress(); // may complete first_upgrade challenge
+  }
+
+  // ---- UI rendering ----------------------------------------
+
+  function updateAcceleratorUI() {
+    const impact = calculateEnvironmentalImpact(acc.personalTokens);
+
+    setAccelText('accelTokens', formatTokenCount(acc.personalTokens));
+    setAccelText('accelDp',     formatDoomPoints(acc.doomPoints));
+
+    // CO₂ display: grams when < 1 kg, otherwise kg
+    const co2Val = impact.co2Kg < 1
+      ? (impact.co2Kg * 1000).toFixed(1) + ' g'
+      : impact.co2Kg.toFixed(2) + ' kg';
+    setAccelText('accelCo2', co2Val);
+
+    // Water display: mL when < 1 L, otherwise L
+    const waterVal = impact.waterL < 1
+      ? Math.round(impact.waterL * 1000) + ' mL'
+      : impact.waterL.toFixed(2) + ' L';
+    setAccelText('accelWater', waterVal);
+
+    updateComboDisplay();
+    updateMilestoneRace();
+    updateBestScore();
+    renderUpgradeShop();
+
+    // Show/hide share button
+    const shareBtn = document.getElementById('shareAccelerationBtn');
+    if (shareBtn) shareBtn.hidden = acc.personalTokens <= 0;
+
+    // Show tap rate
+    const rateEl = document.getElementById('brbTapRate');
+    if (rateEl && acc.tapTimestamps.length >= 2) {
+      const window2s = acc.tapTimestamps.filter((t) => t >= Date.now() - 2000);
+      const rate = window2s.length / 2;
+      rateEl.textContent = rate.toFixed(1) + ' taps/sec';
+    }
+  }
+
+  function setAccelText(id, value) {
+    const el = document.getElementById(id);
+    if (el) el.textContent = value;
+  }
+
+  function updateComboDisplay() {
+    const el = document.getElementById('comboDisplay');
+    const btn = document.getElementById('bigRedButton');
+    const lbl = document.getElementById('brbLabel');
+    if (!el) return;
+
+    el.textContent = acc.combo + '\xD7';
+    el.setAttribute('aria-label', 'Combo multiplier: ' + acc.combo + '\xD7');
+
+    const isMax = acc.combo === 10;
+    el.classList.toggle('combo-max', isMax);
+    if (btn) {
+      btn.classList.toggle('combo-max', isMax);
+      btn.setAttribute('aria-label', 'Feed the Machine \u2014 ' + acc.combo + '\xD7 combo');
+    }
+    if (lbl) {
+      if (acc.combo >= 10)      lbl.textContent = 'MAXIMUM DOOM \u2622\uFE0F';
+      else if (acc.combo >= 5)  lbl.textContent = 'FASTER! \uD83D\uDD25';
+      else if (acc.combo >= 2)  lbl.textContent = 'Keep Going\u2026';
+      else                      lbl.textContent = 'Feed the Machine';
+    }
+  }
+
+  function updateMilestoneRace() {
+    const next = getNextMilestoneForPlayer(acc.personalTokens, MILESTONES);
+    const nameEl = document.getElementById('milestoneRaceName');
+    const pctEl  = document.getElementById('milestoneRacePct');
+    const fill   = document.getElementById('milestoneRaceFill');
+    const bar    = document.getElementById('milestoneRaceBar');
+
+    if (!next) {
+      if (nameEl) nameEl.textContent = 'All cleared \uD83D\uDC80';
+      if (pctEl)  pctEl.textContent  = '100%';
+      if (fill)   fill.style.width   = '100%';
+      return;
+    }
+
+    // Find the previous milestone tokens as the lower bound
+    const idx  = MILESTONES.indexOf(next);
+    const prev = idx > 0 ? MILESTONES[idx - 1].tokens : 0;
+    const pct  = milestoneProgress(acc.personalTokens, prev, next.tokens);
+
+    if (nameEl) nameEl.textContent = next.icon + ' ' + next.name;
+    if (pctEl)  pctEl.textContent  = pct.toFixed(1) + '%';
+    if (fill)   fill.style.width   = pct + '%';
+    if (bar)    bar.setAttribute('aria-valuenow', Math.round(pct));
+
+    // Check if the player just triggered this milestone
+    if (acc.personalTokens >= next.tokens && !acc.personalMilestoneSet.has(next.id)) {
+      acc.personalMilestoneSet.add(next.id);
+      acc.milestonesTriggered++;
+      flashPersonalMilestoneTrigger(next);
+      if (typeof navigator.vibrate === 'function') navigator.vibrate(80);
+      checkAcceleratorAchievements();
+    }
+  }
+
+  function flashPersonalMilestoneTrigger(milestone) {
+    // Flash the race bar
+    const wrap = document.querySelector('.milestone-race-wrap');
+    if (wrap) {
+      wrap.classList.add('milestone-triggered');
+      setTimeout(() => wrap.classList.remove('milestone-triggered'), 700);
+    }
+    // Flash the global milestone card
+    const card = document.getElementById('milestone-' + milestone.id);
+    if (card) {
+      card.classList.add('player-triggered');
+      setTimeout(() => card.classList.remove('player-triggered'), 700);
+    }
+    queueToast({
+      icon: milestone.icon,
+      name: 'Milestone Triggered: ' + milestone.name,
+      desc: 'You personally crossed ' + milestone.shortDesc + '. Catastrophe achieved.',
+    });
+  }
+
+  function updateBestScore() {
+    if (acc.personalTokens > acc.bestScore) {
+      acc.bestScore = acc.personalTokens;
+      saveAcceleratorState();
+      const valueEl = document.getElementById('bestScoreValue');
+      if (valueEl) {
+        valueEl.textContent = formatTokenCount(acc.bestScore);
+        valueEl.className = 'new-record';
+        setTimeout(() => { valueEl.className = ''; }, 2000);
+      }
+    } else {
+      const valueEl = document.getElementById('bestScoreValue');
+      if (valueEl && valueEl.textContent === '\u2014') {
+        valueEl.textContent = acc.bestScore > 0 ? formatTokenCount(acc.bestScore) : '\u2014';
+      }
+    }
+  }
+
+  function renderUpgradeShop() {
+    const shop = document.getElementById('upgradeShop');
+    if (!shop) return;
+
+    shop.innerHTML = '';
+    UPGRADES.forEach((u) => {
+      const owned      = !!acc.ownedUpgrades[u.id];
+      const affordable = acc.doomPoints >= u.cost;
+      const btn        = document.createElement('button');
+      btn.className    = 'upgrade-card' +
+        (owned ? ' owned' : '') +
+        (!owned && !affordable ? ' unaffordable' : '');
+      btn.setAttribute('aria-label', owned
+        ? u.name + ' (owned)'
+        : u.name + ' \u2014 costs ' + u.cost + ' DP'
+      );
+      if (owned) btn.setAttribute('aria-disabled', 'true');
+      btn.innerHTML = `
+        <span class="upgrade-card-icon" aria-hidden="true">${escHtml(u.icon)}</span>
+        <div class="upgrade-card-name">${escHtml(u.name)}</div>
+        <div class="upgrade-card-flavour">${escHtml(u.flavour)}</div>
+        <div class="upgrade-card-cost">${owned ? '\u2713 Owned' : escHtml(String(u.cost)) + ' DP'}</div>
+        <div class="upgrade-card-mult">${escHtml(String(u.multiplier))}\xD7 per tap</div>`;
+      if (!owned) {
+        btn.addEventListener('click', () => purchaseUpgrade(u.id));
+      }
+      shop.appendChild(btn);
+    });
+  }
+
+  function renderChallenges() {
+    const row = document.getElementById('challengeRow');
+    if (!row) return;
+    row.innerHTML = '';
+    acc.challenges.forEach((c) => {
+      const p       = acc.challengeProgress[c.id] || { value: 0, completed: false };
+      const pct     = Math.min(100, (p.value / c.target) * 100);
+      const card    = document.createElement('div');
+      card.className = 'challenge-card' + (p.completed ? ' completed' : '');
+      card.setAttribute('role', 'listitem');
+      card.setAttribute('aria-label', c.label + (p.completed ? ' (completed)' : ''));
+      card.innerHTML = `
+        <span class="challenge-card-icon" aria-hidden="true">${escHtml(c.icon)}</span>
+        <div class="challenge-card-label">${escHtml(c.label)}</div>
+        <div class="challenge-card-desc">${escHtml(c.desc)}</div>
+        <div class="challenge-card-reward">+${escHtml(String(c.rewardDp))} DP</div>
+        <div class="challenge-card-progress">
+          <div class="challenge-card-pct">${pct.toFixed(0)}%</div>
+          <div class="progress-bar" role="progressbar"
+               aria-valuenow="${Math.round(pct)}" aria-valuemin="0" aria-valuemax="100">
+            <div class="progress-fill challenge-progress-fill" style="width:${pct}%"></div>
+          </div>
+        </div>
+        ${p.completed ? '<span class="challenge-checkmark" aria-hidden="true">\u2705</span>' : ''}`;
+      row.appendChild(card);
+    });
+  }
+
+  // ---- Share -----------------------------------------------
+
+  function buildAccelerationShareText() {
+    const impact = calculateEnvironmentalImpact(acc.personalTokens);
+    const co2g   = (impact.co2Kg * 1000).toFixed(1);
+    const waterMl = Math.round(impact.waterL * 1000);
+    const next   = getNextMilestoneForPlayer(acc.personalTokens, MILESTONES);
+    const nextLabel = next ? next.name : 'civilisation collapse';
+    return (
+      '\uD83D\uDE80 I personally accelerated AI\u2019s environmental doom by contributing ' +
+      formatTokenCount(acc.personalTokens) + ' tokens \u2014 ' +
+      co2g + '\u2009g of CO\u2082, ' + waterMl + '\u2009mL of water. ' +
+      'One step closer to ' + nextLabel + '. Come join the apocalypse.\n' +
+      '\u2192 ' + SITE_URL + ' #AccelerateTheDoom #TokenDeathClock'
+    );
+  }
+
+  // ---- Combo reset loop ------------------------------------
+
+  function startComboResetLoop() {
+    setInterval(() => {
+      if (acc.tapTimestamps.length === 0) return;
+      const lastTap = acc.tapTimestamps[acc.tapTimestamps.length - 1];
+      if (Date.now() - lastTap > 1500) {
+        // Reset combo
+        acc.tapTimestamps = [];
+        if (acc.combo !== 1) {
+          acc.combo = 1;
+          updateComboDisplay();
+          const rateEl = document.getElementById('brbTapRate');
+          if (rateEl) rateEl.textContent = 'Tap to begin';
+        }
+      }
+    }, 100);
+  }
+
+  // ---- Init ------------------------------------------------
+
+  function initAccelerator() {
+    loadAcceleratorState();
+
+    // Toggle open/close
+    const toggleBtn = document.getElementById('accelToggleBtn');
+    const content   = document.getElementById('accel-content');
+    if (toggleBtn && content) {
+      toggleBtn.addEventListener('click', () => {
+        const opening = content.hidden;
+        content.hidden = !opening;
+        toggleBtn.textContent = opening
+          ? '\u25BC Close Doom Accelerator'
+          : '\u25BA Open Doom Accelerator';
+        toggleBtn.setAttribute('aria-expanded', opening ? 'true' : 'false');
+        if (opening) {
+          initChallengeProgress();
+          renderChallenges();
+          renderUpgradeShop();
+          updateAcceleratorUI();
+          // Show best score from storage
+          const valueEl = document.getElementById('bestScoreValue');
+          if (valueEl) {
+            valueEl.textContent = acc.bestScore > 0 ? formatTokenCount(acc.bestScore) : '\u2014';
+          }
+        }
+      });
+    }
+
+    // Big Red Button — use pointerdown for instant response on mobile+desktop
+    const btn = document.getElementById('bigRedButton');
+    if (btn) {
+      btn.addEventListener('pointerdown', (e) => {
+        e.preventDefault();
+        handleTap();
+      });
+    }
+
+    // Share button
+    const shareBtn = document.getElementById('shareAccelerationBtn');
+    if (shareBtn) {
+      shareBtn.addEventListener('click', () => {
+        openSharePopup(buildAccelerationShareText());
+        awardBadge('bragging_rights');
+      });
+    }
+
+    // Combo reset timer
+    startComboResetLoop();
+  }
+
   // ---- Bootstrap ------------------------------------------
   function init() {
     // Theme toggle
@@ -1423,6 +1957,7 @@
     initSharePanel();
     initReceiptModal();
     initCalculator();
+    initAccelerator();
 
     // Kick off the live counter RAF loop
     requestAnimationFrame(updateCounters);
diff --git a/styles.css b/styles.css
index 79beb5f..0a2fb22 100644
--- a/styles.css
+++ b/styles.css
@@ -1521,3 +1521,446 @@ footer strong { color: var(--accent-2); }
   .share-doom-options,
   .ai-ticker-text { transition: none; animation: none; }
 }
+
+/* =============================================================
+   ACCELERATE THE DOOM — Styles
+   ============================================================= */
+
+#accelerator-section { background: var(--bg-alt); }
+
+/* ---- Stats Strip ---- */
+.accel-stats-strip {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
+  gap: 0.75rem;
+  margin: 1.25rem 0;
+}
+
+.accel-stat {
+  background: var(--surface);
+  border: 1px solid var(--border);
+  border-radius: 0.5rem;
+  padding: 0.85rem 1rem;
+  text-align: center;
+}
+
+.accel-stat-dp { border-color: var(--accent-2); }
+
+.accel-stat-value {
+  font-family: 'Orbitron', monospace;
+  font-size: clamp(0.9rem, 2.5vw, 1.15rem);
+  font-weight: 700;
+  color: var(--accent-3);
+  line-height: 1.2;
+}
+
+.accel-stat-dp .accel-stat-value { color: var(--accent-2); }
+
+.accel-stat-label {
+  font-size: 0.65rem;
+  color: var(--text-dim);
+  text-transform: uppercase;
+  letter-spacing: 0.08em;
+  margin-top: 0.25rem;
+}
+
+/* ---- Big Red Button ---- */
+.brb-wrap {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 0.75rem;
+  margin: 1.5rem 0;
+}
+
+.combo-display {
+  font-family: 'Orbitron', monospace;
+  font-size: clamp(1.4rem, 5vw, 2.2rem);
+  font-weight: 900;
+  color: var(--accent-2);
+  text-shadow: 0 0 14px rgba(255,136,0,0.5);
+  letter-spacing: 0.05em;
+  min-height: 2.5rem;
+  transition: color 0.1s, text-shadow 0.1s;
+}
+
+.combo-display.combo-max {
+  color: var(--accent);
+  text-shadow: 0 0 20px var(--accent-glow);
+  animation: combo-max-pulse 0.4s ease-in-out infinite alternate;
+}
+
+@keyframes combo-max-pulse {
+  from { text-shadow: 0 0 14px var(--accent-glow); }
+  to   { text-shadow: 0 0 32px var(--accent-glow); }
+}
+
+.big-red-button {
+  /* Minimum 96×96 px for accessibility (WCAG 2.5.5) */
+  width: clamp(96px, 28vw, 168px);
+  height: clamp(96px, 28vw, 168px);
+  border-radius: 50%;
+  border: 3px solid var(--accent);
+  background: radial-gradient(circle at 40% 35%, #3a0000, #1a0000);
+  color: #fff;
+  cursor: pointer;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 0.3rem;
+  box-shadow:
+    0 0 24px var(--accent-glow),
+    inset 0 0 20px rgba(255,51,51,0.08);
+  transition: box-shadow 0.15s, transform 0.1s;
+  position: relative;
+  overflow: hidden;
+  /* Prevent touch delay */
+  touch-action: manipulation;
+  -webkit-tap-highlight-color: transparent;
+  user-select: none;
+}
+
+.big-red-button::before {
+  content: '';
+  position: absolute;
+  inset: 0;
+  border-radius: 50%;
+  background: radial-gradient(circle at 40% 35%, rgba(255,80,80,0.15), transparent 60%);
+  pointer-events: none;
+}
+
+.big-red-button:hover {
+  box-shadow:
+    0 0 40px var(--accent-glow),
+    inset 0 0 28px rgba(255,51,51,0.14);
+  transform: scale(1.04);
+}
+
+.big-red-button:active,
+.big-red-button.tapping {
+  transform: scale(0.94);
+  box-shadow:
+    0 0 56px var(--accent-glow),
+    inset 0 0 40px rgba(255,51,51,0.25);
+}
+
+.big-red-button.combo-max {
+  border-color: var(--accent);
+  box-shadow:
+    0 0 48px var(--accent-glow),
+    0 0 80px rgba(255,51,51,0.2),
+    inset 0 0 32px rgba(255,51,51,0.18);
+  animation: brb-max-glow 0.6s ease-in-out infinite alternate;
+}
+
+@keyframes brb-max-glow {
+  from { box-shadow: 0 0 40px var(--accent-glow), inset 0 0 28px rgba(255,51,51,0.14); }
+  to   { box-shadow: 0 0 72px var(--accent-glow), 0 0 100px rgba(255,51,51,0.25), inset 0 0 40px rgba(255,51,51,0.22); }
+}
+
+.brb-icon {
+  font-size: clamp(1.8rem, 6vw, 2.8rem);
+  line-height: 1;
+  pointer-events: none;
+}
+
+.brb-label {
+  font-family: 'Orbitron', monospace;
+  font-size: clamp(0.48rem, 1.5vw, 0.65rem);
+  font-weight: 700;
+  letter-spacing: 0.06em;
+  color: rgba(255,255,255,0.75);
+  pointer-events: none;
+  text-align: center;
+  padding: 0 0.4rem;
+  line-height: 1.2;
+}
+
+.brb-rate {
+  font-size: 0.72rem;
+  color: var(--text-muted);
+  min-height: 1rem;
+  letter-spacing: 0.06em;
+}
+
+/* ---- Milestone Race Bar ---- */
+.milestone-race-wrap {
+  background: var(--surface);
+  border: 1px solid var(--border);
+  border-radius: 0.5rem;
+  padding: 0.85rem 1.1rem;
+  margin-bottom: 1.5rem;
+}
+
+.milestone-race-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-bottom: 0.5rem;
+  flex-wrap: wrap;
+  gap: 0.25rem;
+}
+
+.milestone-race-label {
+  font-size: 0.78rem;
+  color: var(--text-dim);
+}
+
+.milestone-race-label strong {
+  color: var(--accent-2);
+  font-family: 'Orbitron', monospace;
+  font-size: 0.72rem;
+}
+
+.milestone-race-pct {
+  font-family: 'Orbitron', monospace;
+  font-size: 0.7rem;
+  color: var(--accent-3);
+  font-weight: 700;
+}
+
+.milestone-race-fill {
+  background: linear-gradient(90deg, var(--accent-3), var(--accent-2));
+  transition: width 0.3s ease;
+}
+
+/* Flash when player personally triggers a milestone */
+.milestone-race-wrap.milestone-triggered {
+  animation: race-milestone-flash 0.6s ease-out;
+}
+
+@keyframes race-milestone-flash {
+  0%,100% { border-color: var(--border); }
+  25%,75%  { border-color: var(--accent); box-shadow: 0 0 16px var(--accent-glow); }
+}
+
+/* ---- Section Sub-Titles ---- */
+.accel-section-title {
+  font-family: 'Orbitron', monospace;
+  font-size: 0.78rem;
+  font-weight: 700;
+  letter-spacing: 0.12em;
+  text-transform: uppercase;
+  color: var(--text-dim);
+  margin: 1.25rem 0 0.75rem;
+}
+
+/* ---- Challenge Row ---- */
+.challenge-row {
+  display: flex;
+  gap: 0.75rem;
+  overflow-x: auto;
+  padding-bottom: 0.5rem;
+  scroll-snap-type: x mandatory;
+  -webkit-overflow-scrolling: touch;
+  margin-bottom: 0.5rem;
+}
+
+.challenge-row::-webkit-scrollbar { height: 4px; }
+.challenge-row::-webkit-scrollbar-track { background: var(--surface-2); border-radius: 2px; }
+.challenge-row::-webkit-scrollbar-thumb { background: var(--border); border-radius: 2px; }
+
+.challenge-card {
+  background: var(--surface);
+  border: 1px solid var(--border);
+  border-radius: 0.75rem;
+  padding: 1rem;
+  min-width: 180px;
+  max-width: 220px;
+  flex-shrink: 0;
+  scroll-snap-align: start;
+  position: relative;
+  transition: border-color 0.2s, box-shadow 0.2s;
+}
+
+.challenge-card.completed {
+  border-color: var(--accent-3);
+  box-shadow: 0 0 10px rgba(0,204,119,0.2);
+}
+
+.challenge-card-icon {
+  font-size: 1.5rem;
+  margin-bottom: 0.4rem;
+  display: block;
+}
+
+.challenge-card-label {
+  font-family: 'Orbitron', monospace;
+  font-size: 0.7rem;
+  font-weight: 700;
+  color: var(--text);
+  margin-bottom: 0.3rem;
+  letter-spacing: 0.04em;
+}
+
+.challenge-card-desc {
+  font-size: 0.68rem;
+  color: var(--text-dim);
+  line-height: 1.45;
+  margin-bottom: 0.5rem;
+}
+
+.challenge-card-reward {
+  font-size: 0.65rem;
+  color: var(--accent-2);
+  font-family: 'Orbitron', monospace;
+  font-weight: 700;
+}
+
+.challenge-card-progress {
+  margin-top: 0.5rem;
+}
+
+.challenge-card-pct {
+  font-size: 0.6rem;
+  color: var(--text-muted);
+  text-align: right;
+  margin-bottom: 0.2rem;
+}
+
+.challenge-progress-fill {
+  background: linear-gradient(90deg, var(--accent-4), var(--accent-3));
+  transition: width 0.3s ease;
+}
+
+.challenge-card.completed .challenge-progress-fill {
+  background: var(--accent-3);
+}
+
+.challenge-checkmark {
+  position: absolute;
+  top: 0.5rem;
+  right: 0.6rem;
+  font-size: 1rem;
+}
+
+/* ---- Upgrade Shop ---- */
+.upgrade-shop {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(190px, 1fr));
+  gap: 0.75rem;
+  margin-bottom: 1.25rem;
+}
+
+.upgrade-card {
+  background: var(--surface);
+  border: 1px solid var(--border);
+  border-radius: 0.75rem;
+  padding: 1rem;
+  text-align: center;
+  cursor: pointer;
+  transition: border-color 0.2s, box-shadow 0.2s, transform 0.15s, opacity 0.2s;
+  position: relative;
+}
+
+.upgrade-card:hover:not(:disabled):not(.unaffordable) {
+  border-color: var(--accent-2);
+  box-shadow: 0 0 12px rgba(255,136,0,0.2);
+  transform: translateY(-2px);
+}
+
+.upgrade-card.unaffordable {
+  opacity: 0.4;
+  pointer-events: none;
+}
+
+.upgrade-card.owned {
+  border-color: var(--accent-3);
+  background: var(--bg-alt);
+  cursor: default;
+}
+
+.upgrade-card-icon { font-size: 1.8rem; display: block; margin-bottom: 0.4rem; }
+
+.upgrade-card-name {
+  font-family: 'Orbitron', monospace;
+  font-size: 0.68rem;
+  font-weight: 700;
+  color: var(--text);
+  margin-bottom: 0.3rem;
+  letter-spacing: 0.04em;
+}
+
+.upgrade-card.owned .upgrade-card-name { color: var(--accent-3); }
+
+.upgrade-card-flavour {
+  font-size: 0.65rem;
+  color: var(--text-dim);
+  font-style: italic;
+  line-height: 1.4;
+  margin-bottom: 0.5rem;
+}
+
+.upgrade-card-cost {
+  font-family: 'Orbitron', monospace;
+  font-size: 0.72rem;
+  font-weight: 700;
+  color: var(--accent-2);
+}
+
+.upgrade-card.owned .upgrade-card-cost {
+  color: var(--accent-3);
+}
+
+.upgrade-card-mult {
+  font-size: 0.65rem;
+  color: var(--text-muted);
+  margin-top: 0.15rem;
+}
+
+/* ---- Footer row ---- */
+.accel-footer-row {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  flex-wrap: wrap;
+  gap: 0.75rem;
+  margin-top: 1rem;
+  padding-top: 1rem;
+  border-top: 1px solid var(--border);
+}
+
+.best-score-row {
+  font-size: 0.78rem;
+  color: var(--text-dim);
+}
+
+.best-score-row .new-record {
+  color: var(--accent-2);
+  animation: new-record-flash 0.5s ease-out 3;
+}
+
+@keyframes new-record-flash {
+  0%,100% { opacity: 1; }
+  50%      { opacity: 0.3; }
+}
+
+/* ---- Milestone card "Accelerated by You" flash ---- */
+.milestone-card.player-triggered {
+  animation: player-trigger-flash 0.6s ease-out;
+}
+
+@keyframes player-trigger-flash {
+  0%,100% { box-shadow: 0 0 20px var(--accent-glow); }
+  25%,75%  { box-shadow: 0 0 50px var(--accent-glow), 0 0 80px rgba(255,51,51,0.3); }
+}
+
+/* ---- Responsive ---- */
+@media (max-width: 480px) {
+  .upgrade-shop { grid-template-columns: 1fr 1fr; }
+  .accel-stats-strip { grid-template-columns: 1fr 1fr; }
+}
+
+/* ---- Reduced motion (accelerator additions) ---- */
+@media (prefers-reduced-motion: reduce) {
+  .big-red-button,
+  .big-red-button:hover,
+  .big-red-button:active,
+  .big-red-button.tapping,
+  .big-red-button.combo-max,
+  .combo-display.combo-max,
+  .milestone-race-fill,
+  .challenge-progress-fill,
+  .upgrade-card { transition: none; animation: none; }
+}
diff --git a/tests/death-clock.test.js b/tests/death-clock.test.js
index 111bd8d..1819414 100644
--- a/tests/death-clock.test.js
+++ b/tests/death-clock.test.js
@@ -26,9 +26,14 @@ const {
   generateEquivalences,
   calculatePersonalFootprint,
   sessionEquivalences,
+  getNextMilestoneForPlayer,
+  computeComboMultiplier,
+  getSessionChallenges,
+  formatDoomPoints,
   MILESTONES,
   HISTORICAL_DATA,
   RATE_SCHEDULE,
+  SESSION_CHALLENGE_DEFS,
   BASE_TOKENS,
   TOKENS_PER_SECOND,
 } = core;
@@ -953,3 +958,210 @@ describe('sessionEquivalences', () => {
     expect(large.length).toBeGreaterThanOrEqual(1);
   });
 });
+
+// ============================================================
+// SESSION_CHALLENGE_DEFS
+// ============================================================
+describe('SESSION_CHALLENGE_DEFS', () => {
+  test('is a non-empty array', () => {
+    expect(Array.isArray(SESSION_CHALLENGE_DEFS)).toBe(true);
+    expect(SESSION_CHALLENGE_DEFS.length).toBeGreaterThan(0);
+  });
+
+  test('each challenge has required fields', () => {
+    SESSION_CHALLENGE_DEFS.forEach((c) => {
+      expect(typeof c.id).toBe('string');
+      expect(typeof c.icon).toBe('string');
+      expect(typeof c.label).toBe('string');
+      expect(typeof c.desc).toBe('string');
+      expect(typeof c.type).toBe('string');
+      expect(typeof c.target).toBe('number');
+      expect(c.target).toBeGreaterThan(0);
+      expect(typeof c.rewardDp).toBe('number');
+      expect(c.rewardDp).toBeGreaterThan(0);
+    });
+  });
+
+  test('all challenge ids are unique', () => {
+    const ids = SESSION_CHALLENGE_DEFS.map((c) => c.id);
+    expect(new Set(ids).size).toBe(ids.length);
+  });
+
+  test('has at least 3 challenges (enough to always return a full set of 3)', () => {
+    expect(SESSION_CHALLENGE_DEFS.length).toBeGreaterThanOrEqual(3);
+  });
+});
+
+// ============================================================
+// getNextMilestoneForPlayer
+// ============================================================
+describe('getNextMilestoneForPlayer', () => {
+  test('returns first milestone when personalTokens is 0', () => {
+    const result = getNextMilestoneForPlayer(0, MILESTONES);
+    expect(result).toBe(MILESTONES[0]);
+  });
+
+  test('returns null when personalTokens exceeds all milestones', () => {
+    const huge = MILESTONES[MILESTONES.length - 1].tokens + 1;
+    expect(getNextMilestoneForPlayer(huge, MILESTONES)).toBeNull();
+  });
+
+  test('returns the next uncrossed milestone', () => {
+    const first = MILESTONES[0];
+    const result = getNextMilestoneForPlayer(first.tokens, MILESTONES);
+    expect(result).toBe(MILESTONES[1]);
+  });
+
+  test('returns null for non-numeric tokens', () => {
+    expect(getNextMilestoneForPlayer('abc', MILESTONES)).toBeNull();
+  });
+
+  test('returns null for non-array milestones', () => {
+    expect(getNextMilestoneForPlayer(0, null)).toBeNull();
+  });
+
+  test('works with an empty milestones array', () => {
+    expect(getNextMilestoneForPlayer(0, [])).toBeNull();
+  });
+
+  test('returns the exact milestone at the boundary (not yet crossed)', () => {
+    const threshold = MILESTONES[2].tokens;
+    // tokens = threshold - 1 means milestone 2 is not yet reached
+    const result = getNextMilestoneForPlayer(threshold - 1, MILESTONES);
+    expect(result).toBe(MILESTONES[2]);
+  });
+});
+
+// ============================================================
+// computeComboMultiplier
+// ============================================================
+describe('computeComboMultiplier', () => {
+  test('returns 1 for an empty array', () => {
+    expect(computeComboMultiplier([])).toBe(1);
+  });
+
+  test('returns 1 for a non-array argument', () => {
+    expect(computeComboMultiplier(null)).toBe(1);
+    expect(computeComboMultiplier('abc')).toBe(1);
+  });
+
+  test('returns 1 for a single tap', () => {
+    const now = Date.now();
+    expect(computeComboMultiplier([now])).toBe(1);
+  });
+
+  test('counts taps within the last 1000 ms', () => {
+    const now = 1000000000000;
+    // 5 taps all within the last 1 second
+    const timestamps = [now - 900, now - 700, now - 500, now - 300, now];
+    expect(computeComboMultiplier(timestamps)).toBe(5);
+  });
+
+  test('excludes taps older than 1000 ms', () => {
+    const now = 1000000000000;
+    const timestamps = [now - 2000, now - 1500, now - 100, now];
+    // Only the last 2 are within 1 second of `now`
+    expect(computeComboMultiplier(timestamps)).toBe(2);
+  });
+
+  test('caps at 10 regardless of tap count', () => {
+    const now = Date.now();
+    const timestamps = Array.from({ length: 20 }, (_, i) => now - i * 50);
+    expect(computeComboMultiplier(timestamps)).toBe(10);
+  });
+
+  test('returns 1 if the only tap has an invalid timestamp', () => {
+    expect(computeComboMultiplier([NaN])).toBe(1);
+    expect(computeComboMultiplier(['bad'])).toBe(1);
+  });
+});
+
+// ============================================================
+// getSessionChallenges
+// ============================================================
+describe('getSessionChallenges', () => {
+  test('always returns exactly 3 challenges', () => {
+    expect(getSessionChallenges(Date.now()).length).toBe(3);
+    expect(getSessionChallenges(0).length).toBe(3);
+    expect(getSessionChallenges().length).toBe(3);
+  });
+
+  test('each returned challenge is a valid SESSION_CHALLENGE_DEFS entry', () => {
+    const challenges = getSessionChallenges(Date.now());
+    challenges.forEach((c) => {
+      const found = SESSION_CHALLENGE_DEFS.find((d) => d.id === c.id);
+      expect(found).toBeDefined();
+    });
+  });
+
+  test('returns different challenges for different daily seeds', () => {
+    // Find two seeds that yield different starting indices
+    // Try enough days until we see a difference (wraps at SESSION_CHALLENGE_DEFS.length)
+    const daysToCheck = SESSION_CHALLENGE_DEFS.length;
+    const firstDayMs = 0;
+    const sets = [];
+    for (let d = 0; d < daysToCheck; d++) {
+      sets.push(getSessionChallenges(firstDayMs + d * 86400000).map((c) => c.id).join(','));
+    }
+    const unique = new Set(sets);
+    // With 7 challenges there should be 7 different starting positions
+    expect(unique.size).toBeGreaterThan(1);
+  });
+
+  test('same seed always produces same result', () => {
+    const seed = 1714500000000;
+    const a = getSessionChallenges(seed).map((c) => c.id);
+    const b = getSessionChallenges(seed).map((c) => c.id);
+    expect(a).toEqual(b);
+  });
+
+  test('handles non-numeric seed gracefully', () => {
+    expect(getSessionChallenges('abc').length).toBe(3);
+    expect(getSessionChallenges(null).length).toBe(3);
+  });
+});
+
+// ============================================================
+// formatDoomPoints
+// ============================================================
+describe('formatDoomPoints', () => {
+  test('formats zero', () => {
+    expect(formatDoomPoints(0)).toBe('0 DP');
+  });
+
+  test('formats small integer', () => {
+    expect(formatDoomPoints(42)).toBe('42 DP');
+  });
+
+  test('formats thousands with K suffix', () => {
+    expect(formatDoomPoints(1500)).toBe('1.5K DP');
+  });
+
+  test('omits trailing .0 in K suffix', () => {
+    expect(formatDoomPoints(2000)).toBe('2K DP');
+  });
+
+  test('formats millions with M suffix', () => {
+    expect(formatDoomPoints(2500000)).toBe('2.5M DP');
+  });
+
+  test('omits trailing .0 in M suffix', () => {
+    expect(formatDoomPoints(3000000)).toBe('3M DP');
+  });
+
+  test('returns 0 DP for negative values', () => {
+    expect(formatDoomPoints(-5)).toBe('0 DP');
+  });
+
+  test('returns 0 DP for NaN', () => {
+    expect(formatDoomPoints(NaN)).toBe('0 DP');
+  });
+
+  test('returns 0 DP for non-numeric input', () => {
+    expect(formatDoomPoints('lots')).toBe('0 DP');
+  });
+
+  test('rounds sub-threshold values', () => {
+    expect(formatDoomPoints(9.7)).toBe('10 DP');
+  });
+});