fix: remove alert(), fix waveform zoom, add waveform scroll (wheel + ctrl+wheel)

js/events.js

@@ -214,12 +214,26 @@ export function initEvents() {
     document.getElementById('wave-step').addEventListener('click', manualStep);
 
     document.getElementById('wave-zoom-in').addEventListener('click', () => {
-        state.waveZoom = Math.min(60, state.waveZoom + 5);
+        state.waveZoom = Math.min(100, state.waveZoom + 5);
     });
     document.getElementById('wave-zoom-out').addEventListener('click', () => {
-        state.waveZoom = Math.max(5, state.waveZoom - 5);
+        state.waveZoom = Math.max(2, state.waveZoom - 5);
     });
 
+    // Scroll waveform with mouse wheel
+    document.getElementById('wave-canvas').addEventListener('wheel', e => {
+        e.preventDefault();
+        if (e.ctrlKey || e.metaKey) {
+            // Ctrl+wheel = zoom waveform
+            const delta = e.deltaY > 0 ? -3 : 3;
+            state.waveZoom = Math.max(2, Math.min(100, state.waveZoom + delta));
+        } else {
+            // Wheel = scroll waveform horizontally
+            const scrollDelta = e.deltaY > 0 ? 3 : -3;
+            state.waveScroll = Math.max(0, state.waveScroll + scrollDelta);
+        }
+    }, { passive: false });
+
     // ==================== SIMULATION CONTROLS ====================
     document.getElementById('sim-run-btn').addEventListener('click', () => {
         if (state.simRunning) stopSim(); else startSim();

js/simulation.js

@@ -20,7 +20,7 @@ export function simTick() {
 export function startSim() {
     if (state.simRunning) return;
     const hasClocks = state.gates.some(g => g.type === 'CLOCK');
-    if (!hasClocks) { alert('Place a CLOCK gate first!'); return; }
+    if (!hasClocks) return;
 
     state.simRunning = true;
 

js/waveform.js

@@ -121,11 +121,14 @@ export function drawWaveforms() {
         return;
     }
 
-    // Auto-scroll to show latest
+    // Auto-scroll to show latest (only if we're already near the end)
     const maxVisible = Math.floor(wc.width / state.waveZoom);
-    if (state.timeStep > maxVisible) {
+    const isNearEnd = state.waveScroll >= state.timeStep - maxVisible - 2;
+    if (state.timeStep > maxVisible && isNearEnd) {
         state.waveScroll = state.timeStep - maxVisible;
     }
+    // Clamp scroll to valid range
+    state.waveScroll = Math.max(0, Math.min(state.timeStep - 1, state.waveScroll));
 
     // Draw time grid
     wctx.strokeStyle = '#151520';