#radar-sonar-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;
    font-family: 'Segoe UI', 'Microsoft JhengHei', sans-serif;
    -webkit-font-smoothing: antialiased;
    width: 100%;
}

#radar-sonar-app * { 
    box-sizing: border-box; 
}

#radar-sonar-app .billy-notes-wrapper {
    line-height: 1.6; 
    color: #333; 
    width: 100%; 
    max-width: 1000px;
    margin: 0 auto; 
    padding: 20px; 
    background: transparent;
    min-height: 800px; /* Prevents layout shift */
}

#radar-sonar-app .app-header {
    margin-bottom: 20px;
}

#radar-sonar-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;
}

#radar-sonar-app .subtitle {
    text-align: center; 
    margin-bottom: 20px;
}

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

#radar-sonar-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;
}

#radar-sonar-app .card-header {
    padding: 15px 25px;
    border-bottom: 1px solid var(--slate-200);
    display: flex;
    align-items: center;
    background: #fff;
    gap: 15px;
}

#radar-sonar-app .icon-blue { color: var(--billy-blue); font-size: 1.5em; }
#radar-sonar-app .section-title { font-size: 1.1rem; font-weight: bold; color: var(--slate-800); margin: 0; }

#radar-sonar-app .diagram-container {
    position: relative;
    width: 100%;
    background: #0f172a;
    border-bottom: 1px solid var(--slate-200);
    border-top: 1px solid var(--slate-200);
    padding: 0;
    line-height: 0;
    aspect-ratio: 800 / 240; /* Prevents layout shift before JS loads */
}

#radar-sonar-app canvas {
    display: block;
    width: 100%;
    height: auto;
    max-width: 100%;
}

#radar-sonar-app .sliders-wrapper {
    padding: 20px 25px;
    background: #fff;
    border-bottom: 1px solid var(--slate-200);
}

#radar-sonar-app .slider-group { display: flex; flex-direction: column; gap: 8px; }
#radar-sonar-app .slider-header { display: flex; justify-content: space-between; align-items: center; font-weight: bold; font-size: 0.9rem; color: var(--slate-800); }

#radar-sonar-app input[type=range] {
    -webkit-appearance: none; 
    width: 100%; 
    background: transparent; 
    margin: 10px 0;
}
#radar-sonar-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;
}
#radar-sonar-app input[type=range]::-webkit-slider-runnable-track {
    width: 100%; height: 6px; cursor: pointer; background: var(--slate-200); border-radius: 3px;
}

#radar-sonar-app .btn-start {
    background: linear-gradient(135deg, #F5A623 0%, #F76B1C 100%); color: white;
    box-shadow: 0 4px 10px rgba(245, 166, 35, 0.3); padding: 12px 20px;
    border-radius: 8px; font-weight: 700; cursor: pointer; transition: all 0.2s;
    border: none; display: inline-flex; align-items: center; justify-content: center;
    gap: 8px; width: 100%;
}
#radar-sonar-app .btn-start:hover { transform: translateY(-2px); box-shadow: 0 6px 15px rgba(0, 0, 0, 0.15); }

#radar-sonar-app .info-box {
    padding: 20px; background: #fffbf0; border-left: 5px solid var(--billy-orange);
    border-radius: 0 8px 8px 0; color: #333; font-size: 0.95rem; height: 100%;
}
#radar-sonar-app .info-title { color: var(--billy-blue); font-size: 1.1em; display: flex; align-items: center; gap: 8px; }
#radar-sonar-app .math-display { background: white; padding: 8px; border-radius: 4px; border: 1px solid var(--slate-200); text-align: center; margin-bottom: 16px; overflow-x: auto; box-shadow: 0 1px 2px rgba(0,0,0,0.05); }
#radar-sonar-app .input-label { font-size: 0.75rem; font-weight: 600; color: var(--slate-800); display: block; margin-bottom: 4px; }
#radar-sonar-app .custom-input { width: 100%; padding: 8px 12px; border-radius: 4px; border: 1px solid var(--slate-400); font-size: 0.875rem; outline: none; }
#radar-sonar-app .btn-calc { width: 100%; background: var(--slate-800); color: white; padding: 10px; border-radius: 8px; font-weight: 600; font-size: 0.875rem; border: none; cursor: pointer; transition: background 0.2s; }
#radar-sonar-app .btn-calc:hover { background: #0f172a; }

#radar-sonar-app .toggle-btn {
    flex: 1; display: flex; align-items: center; justify-content: center; gap: 12px;
    padding: 12px 20px; border-radius: 8px; font-weight: bold; transition: all 0.2s; border: 2px solid transparent; cursor: pointer;
}
#radar-sonar-app .active-em { background: #eff6ff; color: #1d4ed8; border-color: #bfdbfe; }
#radar-sonar-app .active-sound { background: #ecfeff; color: #0e7490; border-color: #a5f3fc; }
#radar-sonar-app .inactive { background: #f8fafc; color: var(--slate-500); border-color: var(--slate-200); }
#radar-sonar-app .inactive:hover { background: #f1f5f9; }

#radar-sonar-app .dir-btn { flex: 1; display: flex; flex-direction: column; align-items: center; justify-content: center; padding: 8px; font-size: 0.875rem; font-weight: 500; border-radius: 6px; transition: background 0.2s; border: none; cursor: pointer; }
#radar-sonar-app .active-dir { background: var(--slate-800); color: white; box-shadow: 0 1px 2px rgba(0,0,0,0.1); }
#radar-sonar-app .inactive-dir { background: transparent; color: var(--slate-500); }
#radar-sonar-app .inactive-dir:hover { background: var(--slate-200); }

@media (max-width: 600px) {
    #radar-sonar-app .billy-notes-wrapper { padding: 12px; }
    #radar-sonar-app .card-header, #radar-sonar-app .sliders-wrapper, #radar-sonar-app .info-box { padding: 15px; }
}