diff --git a/src/lib/components/ColourDemonstrator.svelte b/src/lib/components/ColourDemonstrator.svelte
new file mode 100644
index 0000000..501be3e
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+++ b/src/lib/components/ColourDemonstrator.svelte
@@ -0,0 +1,120 @@
+<script lang="ts">
+  import { onMount } from 'svelte';
+  import chroma from 'chroma-js';
+  import { sabbats, type Sabbat } from '$lib/utils/sabbats';
+
+  let simulatedDate = $state(new Date());
+  let isAnimating = $state(false);
+
+  // Re-calculating colours based on Sabbat rotation (similar logic to theme.ts)
+  function getColoursForDate(date: Date) {
+    const year = date.getFullYear();
+    const getSabbatDate = (s: Sabbat, y: number) => new Date(y, s.month - 1, s.day);
+    const allSabbats = [
+      ...sabbats.map((s) => ({ ...s, date: getSabbatDate(s, year - 1) })),
+      ...sabbats.map((s) => ({ ...s, date: getSabbatDate(s, year) })),
+      ...sabbats.map((s) => ({ ...s, date: getSabbatDate(s, year + 1) })),
+    ].sort((a, b) => a.date.getTime() - b.date.getTime());
+
+    let prev = allSabbats[0], next = allSabbats[1];
+    for (let i = 0; i < allSabbats.length - 1; i++) {
+        if (date >= allSabbats[i].date && date < allSabbats[i + 1].date) {
+            prev = allSabbats[i];
+            next = allSabbats[i + 1];
+            break;
+        }
+    }
+
+    const prevDate = prev.date.getTime();
+    const nextDate = next.date.getTime();
+    const progress = (date.getTime() - prevDate) / (nextDate - prevDate);
+
+    // Simplification for demonstrator: interpolate hue
+    let diff = next.rotation - prev.rotation;
+    while (diff > 180) diff -= 360;
+    while (diff < -180) diff += 360;
+    const rotation = (prev.rotation + diff * progress + 360) % 360;
+
+    // Base colours (OKLCH L, C, H)
+    const primary = chroma.oklch(0.69, 0.15, rotation).hex();
+    const secondary = chroma.oklch(0.70, 0.17, (rotation + 45) % 360).hex();
+    const accent = chroma.oklch(0.71, 0.17, (rotation + 90) % 360).hex();
+
+    return { primary, secondary, accent, prevName: prev.name, nextName: next.name, progress };
+  }
+
+  let colours = $derived(getColoursForDate(simulatedDate));
+
+  // Animation loop
+  onMount(() => {
+    let frame: number;
+    function animate() {
+      if (isAnimating) {
+        simulatedDate = new Date(simulatedDate.getTime() + 1000 * 60 * 60 * 24 * 2); // Advance 2 days per frame
+        frame = requestAnimationFrame(animate);
+      }
+    }
+    if (isAnimating) animate();
+    return () => cancelAnimationFrame(frame);
+  });
+
+  $effect(() => {
+    if (isAnimating) {
+      let frame = requestAnimationFrame(function loop() {
+          simulatedDate = new Date(simulatedDate.getTime() + 1000 * 60 * 60 * 24 * 2);
+          if (isAnimating) frame = requestAnimationFrame(loop);
+      });
+      return () => cancelAnimationFrame(frame);
+    }
+  });
+</script>
+
+<div class="demo-container">
+  <div class="swatches">
+    <div class="swatch" style="background: {colours.primary}">Primary</div>
+    <div class="swatch" style="background: {colours.secondary}">Secondary</div>
+    <div class="swatch" style="background: {colours.accent}">Accent</div>
+  </div>
+  
+  <div class="controls">
+    <label>
+      Date: {simulatedDate.toLocaleDateString('en-gb')}
+      <input type="range" min={new Date(2026, 0, 1).getTime()} max={new Date(2027, 0, 1).getTime()} 
+             value={simulatedDate.getTime()} oninput={(e) => simulatedDate = new Date(Number(e.currentTarget.value))} />
+    </label>
+    <button onclick={() => isAnimating = !isAnimating}>
+      {isAnimating ? 'Stop' : 'Animate'}
+    </button>
+  </div>
+  <p class="status">Transitioning from {colours.prevName} to {colours.nextName}</p>
+</div>
+
+<style>
+  .demo-container {
+    padding: var(--space-md);
+    border: 1px solid var(--surface-color);
+    border-radius: var(--radius-lg);
+    background: var(--surface-raised);
+    display: flex;
+    flex-direction: column;
+    gap: var(--space-md);
+  }
+  .swatches {
+    display: grid;
+    grid-template-columns: repeat(3, 1fr);
+    gap: var(--space-sm);
+  }
+  .swatch {
+    height: 100px;
+    border-radius: var(--radius-sm);
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    color: white;
+    font-weight: 800;
+    font-size: var(--text-xs);
+    text-shadow: 0 1px 2px rgba(0,0,0,0.2);
+  }
+  .controls { display: flex; flex-direction: column; gap: var(--space-xs); }
+  .status { font-family: var(--font-mono); font-size: var(--text-xs); margin: 0; color: var(--color-text-600); }
+</style>