#diffraction-sim-app {
    --billy-orange: #F5A623; 
    --billy-dark: #333; 
    --billy-blue: #008080; 
    --bg-light: #f9f9f9; 
    --slate-200: #e2e8f0;
    --slate-400: #94a3b8;
    --slate-500: #64748b;
    --slate-800: #1e293b;
    --indigo-500: #6366f1;
    font-family: 'Segoe UI', 'Microsoft JhengHei', sans-serif;
    -webkit-font-smoothing: antialiased;
    width: 100%;
}

#diffraction-sim-app * { box-sizing: border-box; }

#diffraction-sim-app .billy-notes-wrapper {
    line-height: 1.6; 
    color: #333; 
    width: 100%; 
    max-width: 900px;
    margin: 0 auto; 
    padding: 20px; 
    background: transparent;
    min-height: 800px; /* Prevents layout shift */
}

#diffraction-sim-app .app-header { margin-bottom: 20px; }
#diffraction-sim-app .main-title { 
    color: var(--billy-blue); 
    border-bottom: 3px solid var(--billy-orange); 
    padding-bottom: 10px; 
    font-size: 2em; 
    text-align: center; 
    margin-bottom: 20px; 
    margin-top: 0; 
    font-weight: bold;
}
#diffraction-sim-app .subtitle { text-align: center; margin-bottom: 20px; }

#diffraction-sim-app .zh-text { color: #666; font-size: 0.9em; display: block; margin-top: 4px; font-weight: normal; }
#diffraction-sim-app .small-zh { font-size: 0.85em; }
#diffraction-sim-app .inline-zh { display: inline; font-size: 0.85em; color: inherit; }

#diffraction-sim-app .note-card { 
    background: var(--bg-light); 
    border-radius: 12px; 
    padding: 0; 
    margin: 20px 0; 
    box-shadow: 0 4px 15px rgba(0,0,0,0.05); 
    border-top: 4px solid var(--billy-blue); 
    overflow: hidden;
}

#diffraction-sim-app .card-header {
    padding: 15px 25px; border-bottom: 1px solid var(--slate-200);
    display: flex; align-items: center; background: #fff; gap: 15px;
}
#diffraction-sim-app .icon-blue { color: var(--billy-blue); font-size: 1.5em; }
#diffraction-sim-app .section-title { font-size: 1.1rem; font-weight: bold; color: var(--slate-800); margin: 0; }

#diffraction-sim-app .diagram-container {
    position: relative; width: 100%; background: #0f172a;
    border-bottom: 1px solid var(--slate-200); padding: 20px;
    display: flex; justify-content: center; align-items: center;
    margin: 0;
}
#diffraction-sim-app canvas#sim-canvas {
    display: block; width: 100%; max-width: 400px; aspect-ratio: 1 / 1;
    image-rendering: pixelated; border-radius: 8px; box-shadow: 0 0 20px rgba(0,0,0,0.5);
}
#diffraction-sim-app .overlay-info {
    position: absolute; top: 10px; left: 10px; background: rgba(0,0,0,0.6);
    color: white; padding: 5px 10px; border-radius: 4px; font-family: monospace;
    font-size: 0.85rem; pointer-events: none;
}

#diffraction-sim-app .chart-container {
    padding: 20px; background: #fff; height: 300px; width: 100%;
    border-bottom: 1px solid var(--slate-200); margin: 0;
}

#diffraction-sim-app .sliders-wrapper {
    padding: 25px; background: #fff; display: grid; grid-template-columns: 1fr 1fr; gap: 25px; margin: 0;
}
#diffraction-sim-app fieldset { border: none; padding: 0; margin: 0; }
#diffraction-sim-app .control-section { display: flex; flex-direction: column; gap: 15px; }
#diffraction-sim-app .slider-group { display: flex; flex-direction: column; gap: 8px; }
#diffraction-sim-app .slider-header { display: flex; justify-content: space-between; align-items: center; font-weight: bold; font-size: 0.9rem; color: var(--slate-800); margin-bottom: 0.5rem; }
#diffraction-sim-app .mb-2 { margin-bottom: 0.5rem; }

#diffraction-sim-app .val-badge {
    background: var(--bg-light); border: 1px solid var(--slate-200);
    padding: 2px 6px; border-radius: 4px; font-family: monospace;
    font-size: 0.85rem; color: var(--billy-blue);
}

#diffraction-sim-app input[type=range] {
    -webkit-appearance: none; width: 100%; background: transparent; margin: 8px 0;
}
#diffraction-sim-app input[type=range]::-webkit-slider-thumb {
    -webkit-appearance: none; height: 18px; width: 18px; border-radius: 50%;
    background: var(--billy-blue); cursor: pointer; margin-top: -6px; 
    box-shadow: 0 2px 4px rgba(0,0,0,0.2); border: 2px solid white;
}
#diffraction-sim-app input[type=range]::-webkit-slider-runnable-track {
    width: 100%; height: 6px; cursor: pointer; background: var(--slate-200); border-radius: 3px;
}
#diffraction-sim-app .spectrum-bar {
    height: 8px; width: 100%; border-radius: 4px;
    background: linear-gradient(to right, #8b5cf6, #3b82f6, #10b981, #eab308, #ef4444);
    margin-top: -4px; opacity: 0.8;
}

#diffraction-sim-app .toggle-row { display: flex; gap: 10px; margin-bottom: 10px; }
#diffraction-sim-app .toggle-btn {
    flex: 1; padding: 10px; border-radius: 8px; font-weight: bold; font-size: 0.9rem;
    cursor: pointer; transition: all 0.2s; border: 2px solid var(--slate-200);
    background: var(--bg-light); color: var(--slate-500); display: flex;
    flex-direction: column; align-items: center; justify-content: center; gap: 4px;
}
#diffraction-sim-app .toggle-btn.active { background: #eff6ff; color: var(--billy-blue); border-color: #bfdbfe; }
#diffraction-sim-app .toggle-btn i { font-size: 1.2rem; }

#diffraction-sim-app .info-box {
    margin: 0 25px 25px 25px; padding: 20px; background: #fffbf0;
    border-left: 5px solid var(--billy-orange); border-radius: 0 8px 8px 0;
    color: #333; font-size: 0.95rem;
}

@media (max-width: 768px) {
    #diffraction-sim-app .sliders-wrapper { grid-template-columns: 1fr; }
}