Add signal source selector to oscilloscope hero

Source knob cycles through 6 tracks: the original CC-licensed
Spirals intro plus 5 N-Spheres tracks (Function, Intersect,
Attractor, Flux, Core) by Fenderson & Hansi3D.

- 48kHz FLAC conversions served via git LFS (~189MB total)
- Rotary knob with CSS custom property composable transforms
- Dynamic attribution (CC link for Spirals, album credit for N-Spheres)
- Signal selection persisted in localStorage
- Loading state overlay while buffering larger tracks
- Skin-aware labels (465: "Source", 545A: "Input")
- Keyboard accessible (Enter/Space to cycle)

.gitattributes

@@ -0,0 +1 @@
+docs/public/n-spheres/*.flac filter=lfs diff=lfs merge=lfs -text

docs/src/components/OscilloscopeDisplay.astro

@@ -41,6 +41,14 @@
   <!-- Control panel -->
   <div class="scope-panel">
     <div class="scope-controls-row">
+      <!-- SOURCE section -->
+      <div class="scope-section">
+        <span class="scope-section-label">Source</span>
+        <div class="scope-knob scope-source-knob" id="scope-source-knob"
+             role="button" tabindex="0" aria-label="Select signal source"></div>
+        <span class="scope-knob-label scope-source-name" id="scope-source-name">Spirals</span>
+      </div>
+
       <!-- VERTICAL section -->
       <div class="scope-section">
         <span class="scope-section-label">Vertical</span>
@@ -72,12 +80,7 @@
 
   <!-- Attribution -->
   <div class="scope-attribution-bar">
-    <div class="scope-attribution">
-      "<a href="http://oscilloscopemusic.com/" target="_blank" rel="noopener">Spirals</a>" by Jerobeam Fenderson
-      (<a href="https://creativecommons.org/licenses/by-nc-sa/4.0/" target="_blank" rel="noopener license">CC BY-NC-SA</a>)
-      · Visual: <a href="https://codepen.io/2Mogs" target="_blank" rel="noopener">Nick Watton</a>
-      · <a href="https://gist.github.com/rsp2k/ac68b1bb290b8124e162987ed1df8d53" target="_blank" rel="noopener">rsp2k</a>
-    </div>
+    <div class="scope-attribution" id="scope-attribution"></div>
   </div>
 
   <!-- Ventilation holes (545A skin only — hidden by default) -->
@@ -100,10 +103,20 @@
 <audio id="scope-audio" src="/spirals_shrt.mp3" loop preload="none"></audio>
 
 <script>
+  // ── Signal configuration ──────────────────────────────────
+  const SIGNALS = [
+    { id: 'spirals',   name: 'Spirals',   src: '/spirals_shrt.mp3', artist: 'Jerobeam Fenderson', license: 'CC BY-NC-SA 4.0', link: 'http://oscilloscopemusic.com/' },
+    { id: 'function',  name: 'Function',  src: '/n-spheres/function.flac',  artist: 'Fenderson & Hansi3D', album: 'N-Spheres' },
+    { id: 'intersect', name: 'Intersect', src: '/n-spheres/intersect.flac', artist: 'Fenderson & Hansi3D', album: 'N-Spheres' },
+    { id: 'attractor', name: 'Attractor', src: '/n-spheres/attractor.flac', artist: 'Fenderson & Hansi3D', album: 'N-Spheres' },
+    { id: 'flux',      name: 'Flux',      src: '/n-spheres/flux.flac',      artist: 'Fenderson & Hansi3D', album: 'N-Spheres' },
+    { id: 'core',      name: 'Core',      src: '/n-spheres/core.flac',      artist: 'Fenderson & Hansi3D', album: 'N-Spheres' },
+  ] as const;
+
   // ── Skin configuration ────────────────────────────────────
   const SKINS: Record<string, { brand: string; model: string; sub: string; sections: string[] }> = {
-    '465':  { brand: 'Tektronix', model: 'mcltspice',   sub: '',             sections: ['Vertical', 'Horizontal', 'Trigger'] },
-    '545a': { brand: 'Tektronix', model: 'Type 545A',   sub: 'Oscilloscope', sections: ['Vert Ampl', 'Sweep', 'Trigger'] },
+    '465':  { brand: 'Tektronix', model: 'mcltspice',   sub: '',             sections: ['Source', 'Vertical', 'Horizontal', 'Trigger'] },
+    '545a': { brand: 'Tektronix', model: 'Type 545A',   sub: 'Oscilloscope', sections: ['Input', 'Vert Ampl', 'Sweep', 'Trigger'] },
   };
   const SKIN_ORDER = Object.keys(SKINS);
 
@@ -141,7 +154,7 @@
         brandSub.style.display = skin.sub ? '' : 'none';
       }
 
-      // Update section labels (Vertical/Vert Ampl, etc.)
+      // Update section labels (Source/Input, Vertical/Vert Ampl, etc.)
       sectionLabels.forEach((label, i) => {
         if (skin.sections[i]) label.textContent = skin.sections[i];
       });
@@ -161,6 +174,95 @@
     });
   }
 
+  // ── Signal source selector ────────────────────────────────
+  function initSignal(audio: HTMLAudioElement, screen: HTMLElement) {
+    const sourceKnob = document.getElementById('scope-source-knob');
+    const sourceName = document.getElementById('scope-source-name');
+
+    if (!sourceKnob || !sourceName) return;
+    // Guard against double-init
+    if (sourceKnob.dataset.signalInit) return;
+    sourceKnob.dataset.signalInit = 'true';
+
+    let signalIndex = parseInt(localStorage.getItem('scope-signal') || '0', 10);
+    if (signalIndex < 0 || signalIndex >= SIGNALS.length) signalIndex = 0;
+
+    function applySignal(idx: number, shouldPlay: boolean) {
+      const signal = SIGNALS[idx];
+      signalIndex = idx;
+
+      // Update source name label
+      sourceName!.textContent = signal.name;
+
+      // Rotate knob indicator to reflect position (custom prop composes with CSS hover scale)
+      const rotation = (idx / SIGNALS.length) * 270 - 135;
+      sourceKnob!.style.setProperty('--knob-rotation', `${rotation}deg`);
+
+      // Update attribution
+      renderAttribution(signal);
+
+      // Persist selection
+      localStorage.setItem('scope-signal', String(idx));
+
+      // Update audio source
+      const wasPlaying = !audio.paused;
+      if (wasPlaying || shouldPlay) {
+        screen.dataset.loading = 'true';
+        audio.pause();
+      }
+
+      audio.src = signal.src;
+      audio.load();
+
+      if (wasPlaying || shouldPlay) {
+        const onCanPlay = () => {
+          audio.removeEventListener('canplay', onCanPlay);
+          screen.dataset.loading = 'false';
+          audio.play().catch(e => console.error('Signal playback failed:', e));
+        };
+        audio.addEventListener('canplay', onCanPlay);
+
+        // Timeout fallback — don't leave loading state indefinitely
+        setTimeout(() => {
+          screen.dataset.loading = 'false';
+        }, 15000);
+      }
+    }
+
+    // Click cycles to next signal
+    sourceKnob.addEventListener('click', () => {
+      const next = (signalIndex + 1) % SIGNALS.length;
+      applySignal(next, false);
+    });
+
+    // Keyboard: Enter/Space to cycle
+    sourceKnob.addEventListener('keydown', (e: KeyboardEvent) => {
+      if (e.key === 'Enter' || e.key === ' ') {
+        e.preventDefault();
+        const next = (signalIndex + 1) % SIGNALS.length;
+        applySignal(next, false);
+      }
+    });
+
+    // Apply saved signal on init (don't auto-play)
+    applySignal(signalIndex, false);
+
+    return { applySignal, getIndex: () => signalIndex };
+  }
+
+  function renderAttribution(signal: typeof SIGNALS[number]) {
+    const el = document.getElementById('scope-attribution');
+    if (!el) return;
+
+    const visualCredit = '· Visual: <a href="https://codepen.io/2Mogs" target="_blank" rel="noopener">Nick Watton</a> · <a href="https://gist.github.com/rsp2k/ac68b1bb290b8124e162987ed1df8d53" target="_blank" rel="noopener">rsp2k</a>';
+
+    if ('license' in signal && signal.license) {
+      el.innerHTML = `&ldquo;<a href="${signal.link}" target="_blank" rel="noopener">${signal.name}</a>&rdquo; by ${signal.artist} (<a href="https://creativecommons.org/licenses/by-nc-sa/4.0/" target="_blank" rel="noopener license">CC BY-NC-SA</a>) ${visualCredit}`;
+    } else {
+      el.innerHTML = `&ldquo;${signal.name}&rdquo; from <em>${('album' in signal) ? signal.album : ''}</em> by ${signal.artist} ${visualCredit}`;
+    }
+  }
+
   // ── Oscilloscope XY renderer ──────────────────────────────
   // Uses AnalyserNode (modern Web Audio) instead of deprecated ScriptProcessor
   function initScope() {
@@ -178,6 +280,9 @@
     // Draw idle state: faint center dot
     drawIdle(ctx, canvas.width, canvas.height);
 
+    // Init signal source selector
+    initSignal(audio, screen);
+
     let audioCtx: AudioContext | null = null;
     let analyserL: AnalyserNode | null = null;
     let analyserR: AnalyserNode | null = null;

docs/src/styles/oscilloscope.css

@@ -240,6 +240,51 @@
   line-height: 1;
 }
 
+/* ── Source knob (interactive) ───────────────────────────── */
+/* Uses --knob-rotation custom prop so JS rotation composes with CSS scale */
+.scope-source-knob {
+  cursor: pointer;
+  transition: transform 0.15s;
+  transform: rotate(var(--knob-rotation, 0deg));
+}
+
+.scope-source-knob:hover {
+  transform: rotate(var(--knob-rotation, 0deg)) scale(1.08);
+}
+
+.scope-source-knob:active {
+  transform: rotate(var(--knob-rotation, 0deg)) scale(0.95);
+}
+
+.scope-source-knob:focus-visible {
+  outline: 2px solid var(--scope-teal);
+  outline-offset: 2px;
+}
+
+/* ── Signal name label ──────────────────────────────────── */
+.scope-source-name {
+  max-width: 60px;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+  text-align: center;
+}
+
+/* ── Loading state overlay ──────────────────────────────── */
+.scope-screen[data-loading="true"]::after {
+  content: '';
+  position: absolute;
+  inset: 0;
+  background: rgba(10, 10, 10, 0.7);
+  z-index: 5;
+  animation: scope-loading-pulse 1.2s ease-in-out infinite;
+}
+
+@keyframes scope-loading-pulse {
+  0%, 100% { opacity: 0.5; }
+  50% { opacity: 0.9; }
+}
+
 /* ── Power toggle ────────────────────────────────────────── */
 .scope-toggle {
   appearance: none;