diff --git a/README.md b/README.md
index 3a57190..d281fb9 100644
--- a/README.md
+++ b/README.md
@@ -197,6 +197,7 @@ Two important conventions:
 | `motion.js` | `prefers-reduced-motion` matchMedia gate, live-updates | `prefersReducedMotion` |
 | `analytics.js` | Thin wrapper over Umami, with once-per-session helper | `trackEvent`, `trackOnce` |
 | `stats.js` | Collective-distance API client (Turso-backed via /api/distance) | `fetchTotalDistance`, `reportSessionDistance` |
+| `milestones.js` | Distance threshold table + once-per-session edge detection | `MILESTONES`, `checkMilestone` |
 
 ---
 
@@ -323,6 +324,7 @@ Tracked events:
 | `max-speed` | First time speed reaches MAX_SPEED, once per session | `{ distance }` |
 | `first-near-miss` | First NEAR MISS trigger, once per session | `{ distance }` |
 | `music-mute` / `music-unmute` | Each click on the ♪ button | – |
+| `milestone-reached` | Each time the rocket crosses a new distance threshold | `{ au }` |
 
 Distances are integer AU. Nothing user-identifying is sent. Remove the Umami script tag (or fork without it) if you'd rather not be counted.
 
diff --git a/index.html b/index.html
index abf5001..a4779e2 100644
--- a/index.html
+++ b/index.html
@@ -68,6 +68,11 @@ <h1>LITTLE ROCKET</h1>
 
   <div id="near-miss" hidden>NEAR MISS</div>
 
+  <div id="milestone-toast" hidden aria-live="polite">
+    <span id="milestone-distance" class="milestone-distance"></span>
+    <span id="milestone-label" class="milestone-label"></span>
+  </div>
+
   <div id="throttle-bar" hidden aria-hidden="true">
     <div id="throttle-fill"></div>
   </div>
diff --git a/src/main.js b/src/main.js
index d970b01..1ab253b 100644
--- a/src/main.js
+++ b/src/main.js
@@ -31,6 +31,7 @@ import { initMusic, startMusic, toggleMusic, isMuted, hasMusic } from './music.j
 import { startStory } from './story.js';
 import { trackOnce, trackEvent } from './analytics.js';
 import { fetchTotalDistance, reportSessionDistance } from './stats.js';
+import { checkMilestone } from './milestones.js';
 
 const ROT_SPEED = 0.02;        // radians per 60fps-frame
 const ACCEL     = 0.05;        // speed delta per 60fps-frame
@@ -56,6 +57,8 @@ fetchTotalDistance().then((stats) => {
 const HINT_VISIBLE_MS = 6000;
 const HINT_FADE_MS = 400; // matches --ij-duration-slow in CSS
 const NEAR_MISS_VISIBLE_MS = 700;
+const MILESTONE_VISIBLE_MS = 3200;
+const MILESTONE_FADE_MS = 600; // matches CSS transition
 const INTRO_DURATION = 1.6;     // seconds of cinematic intro before player takes control
 const INTRO_FOV_START = 50;     // narrow FOV → opens up to FOV_IDLE
 const INTRO_CAM_DISTANCE = 60;  // how far back the camera starts behind the rocket
@@ -168,6 +171,26 @@ function run() {
     }, NEAR_MISS_VISIBLE_MS);
     trackOnce('first-near-miss', { distance: Math.floor(distanceAU) });
   }
+
+  const milestoneEl = document.getElementById('milestone-toast');
+  const milestoneDistanceEl = document.getElementById('milestone-distance');
+  const milestoneLabelEl = document.getElementById('milestone-label');
+  let milestoneHideTimer = null;
+  let milestoneRemoveTimer = null;
+  function flashMilestone(milestone) {
+    if (milestoneHideTimer) clearTimeout(milestoneHideTimer);
+    if (milestoneRemoveTimer) clearTimeout(milestoneRemoveTimer);
+    milestoneDistanceEl.textContent = `${milestone.au.toLocaleString()} AU`;
+    milestoneLabelEl.textContent = milestone.label;
+    milestoneEl.hidden = false;
+    void milestoneEl.offsetWidth;
+    milestoneEl.classList.add('visible');
+    milestoneHideTimer = setTimeout(() => {
+      milestoneEl.classList.remove('visible');
+      milestoneRemoveTimer = setTimeout(() => { milestoneEl.hidden = true; }, MILESTONE_FADE_MS);
+    }, MILESTONE_VISIBLE_MS);
+    trackEvent('milestone-reached', { au: milestone.au });
+  }
   const clock = new THREE.Clock();
   const forward = new THREE.Vector3();
   const camOffset = new THREE.Vector3();
@@ -255,6 +278,7 @@ function run() {
     speedEl.textContent = speed.toFixed(1);
     distanceAU += speed * realDt;
     distanceEl.textContent = `${Math.floor(distanceAU)} AU`;
+    checkMilestone(distanceAU, flashMilestone);
     if (isTouch && introDone) {
       throttleFill.style.height = `${(speed / MAX_SPEED) * 100}%`;
     }
diff --git a/src/milestones.js b/src/milestones.js
new file mode 100644
index 0000000..41aba26
--- /dev/null
+++ b/src/milestones.js
@@ -0,0 +1,31 @@
+/**
+ * Distance milestones — fire celebratory HUD toasts at round-number AU
+ * thresholds. Each milestone fires at most once per session; reload to see
+ * them again.
+ *
+ * Tuned to feel like genuine landmarks rather than every other minute:
+ * the first one rewards a few minutes of flying, the rest space out
+ * exponentially so a long flight always has a next thing to chase.
+ */
+
+export const MILESTONES = [
+  { au: 100,     label: 'Past Pluto' },
+  { au: 1000,    label: 'Through the heliosphere' },
+  { au: 10000,   label: 'Into the Oort cloud' },
+  { au: 100000,  label: 'One light-year out' },
+];
+
+const fired = new Set();
+
+/**
+ * Call once per frame. If the rocket has just crossed any unfired milestone
+ * threshold, invokes onTrigger(milestone) — once per threshold per session.
+ */
+export function checkMilestone(distanceAU, onTrigger) {
+  for (const m of MILESTONES) {
+    if (distanceAU >= m.au && !fired.has(m.au)) {
+      fired.add(m.au);
+      onTrigger(m);
+    }
+  }
+}
diff --git a/styles/main.css b/styles/main.css
index 7224af5..ff6df25 100644
--- a/styles/main.css
+++ b/styles/main.css
@@ -274,6 +274,52 @@ h1 {
 #near-miss[hidden] { display: none; }
 #near-miss.visible { opacity: 1; }
 
+/* Milestone toast — fires once per session when the rocket crosses a round
+   AU threshold. Bigger and more present than the near-miss flash, but still
+   non-blocking and pointer-event-free. */
+#milestone-toast {
+  position: fixed;
+  top: 28%;
+  left: 50%;
+  transform: translateX(-50%);
+  padding: var(--ij-spacing-lg, 16px) var(--ij-spacing-xxxl, 32px);
+  background: rgba(0, 0, 0, 0.78);
+  border: 2px solid var(--ij-color-primary, #D0FF00);
+  border-radius: var(--ij-radius-md, 12px);
+  box-shadow: 0 0 32px rgba(208, 255, 0, 0.28);
+  text-align: center;
+  pointer-events: none;
+  opacity: 0;
+  transition: opacity 600ms var(--ij-easing-emphasized,
+    cubic-bezier(0.2, 0, 0, 1));
+}
+#milestone-toast[hidden] { display: none; }
+#milestone-toast.visible { opacity: 1; }
+
+.milestone-distance {
+  display: block;
+  font-size: var(--ij-font-size-xl, 24px);
+  font-weight: var(--ij-font-weight-bold, 700);
+  color: var(--ij-color-primary, #D0FF00);
+  letter-spacing: 2px;
+  font-variant-numeric: tabular-nums;
+}
+
+.milestone-label {
+  display: block;
+  margin-top: var(--ij-spacing-xs, 4px);
+  font-size: var(--ij-font-size-sm, 14px);
+  color: var(--ij-color-text-secondary, rgba(255, 255, 255, 0.78));
+  letter-spacing: 1.5px;
+  text-transform: uppercase;
+}
+
+@media (max-width: 480px) {
+  .milestone-distance { font-size: var(--ij-font-size-lg, 18px); }
+  .milestone-label    { font-size: var(--ij-font-size-xs, 12px); }
+  #milestone-toast    { padding: var(--ij-spacing-md, 12px) var(--ij-spacing-xl, 20px); }
+}
+
 /* Throttle bar: vertical fill on the right edge that mirrors current speed.
    Visible only on touch devices (no benefit when keyboard handles throttle). */
 #throttle-bar {