/* ===== CSS Variables & Reset ===== */
:root {
    --bg-primary: #f0f4f8;
    --bg-secondary: #ffffff;
    --bg-tertiary: #e8eef4;
    --text-primary: #1a1a2e;
    --text-secondary: #5a6270;
    --border-color: #d0d8e0;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.08);

    /* Electrolysis Colors */
    --cathode-color: #5a6270;
    --anode-color: #e74c3c;
    --hydrogen-color: #ecf0f1;
    --oxygen-color: #e74c3c;
    --water-color: #3498db;
    --electron-color: #f1c40f;
    --accent-color: #3498db;

    --radius: 12px;
    --transition: all 0.3s ease;
}

[data-theme="dark"] {
    --bg-primary: #0f0f1a;
    --bg-secondary: #1a1a2e;
    --bg-tertiary: #252540;
    --text-primary: #f0f4f8;
    --text-secondary: #a0a8b8;
    --border-color: #2a2a45;
    --shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    transition: var(--transition);
}

/* ===== App Container ===== */
.app-container {
    max-width: 1800px;
    margin: 0 auto;
    padding: 15px;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ===== Header ===== */
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 25px;
    background: var(--bg-secondary);
    border-radius: var(--radius);
    margin-bottom: 15px;
    box-shadow: var(--shadow);
}

.header h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: #3498db;
}

.header-controls {
    display: flex;
    gap: 10px;
}

.control-btn {
    width: 42px;
    height: 42px;
    border: 2px solid var(--border-color);
    border-radius: 50%;
    background: var(--bg-primary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.control-btn:hover {
    border-color: var(--accent-color);
    transform: scale(1.05);
}

.control-btn svg {
    width: 20px;
    height: 20px;
    color: var(--text-primary);
}

.moon-icon {
    display: none;
}

[data-theme="dark"] .sun-icon {
    display: none;
}

[data-theme="dark"] .moon-icon {
    display: block;
}

.compress-icon {
    display: none;
}

.fullscreen-active .expand-icon {
    display: none;
}

.fullscreen-active .compress-icon {
    display: block;
}

/* ===== Main Content ===== */
.main-content {
    display: grid;
    grid-template-columns: 240px 1fr 280px;
    gap: 15px;
    flex: 1;
}

/* ===== Controls Panel ===== */
.controls-panel {
    background: var(--bg-secondary);
    border-radius: var(--radius);
    padding: 20px;
    box-shadow: var(--shadow);
    display: flex;
    flex-direction: column;
    gap: 18px;
}

.controls-panel h2 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
}

.control-section h3 {
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 10px;
    text-transform: uppercase;
}

/* Voltage Display */
.voltage-display {
    text-align: center;
    padding: 15px;
    background: linear-gradient(135deg, #3498db, #2980b9);
    border-radius: 12px;
    color: white;
}

.voltage-value {
    font-size: 2.5rem;
    font-weight: 800;
}

.voltage-unit {
    font-size: 1.2rem;
    font-weight: 600;
}

.voltage-slider {
    width: 100%;
    height: 12px;
    border-radius: 6px;
    background: linear-gradient(to right, #bdc3c7, #3498db, #e74c3c);
    -webkit-appearance: none;
    margin: 10px 0;
}

.voltage-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: white;
    border: 3px solid var(--text-primary);
    cursor: pointer;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
}

.voltage-labels {
    display: flex;
    justify-content: space-between;
    font-size: 0.75rem;
    color: var(--text-secondary);
}

/* Playback Buttons */
.playback-buttons {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.playback-btn {
    padding: 12px;
    background: var(--bg-tertiary);
    border: 2px solid transparent;
    border-radius: 10px;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-primary);
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.playback-btn:hover {
    border-color: var(--accent-color);
}

.playback-btn.primary {
    background: linear-gradient(135deg, #27ae60, #2ecc71);
    color: white;
}

.playback-btn.primary:hover {
    transform: scale(1.02);
}

.playback-btn.primary.playing {
    background: linear-gradient(135deg, #e74c3c, #c0392b);
}

.pause-icon {
    display: none;
}

.playback-btn.primary.playing .play-icon {
    display: none;
}

.playback-btn.primary.playing .pause-icon {
    display: inline;
}

.playback-btn.primary.playing .btn-text::after {
    content: 'Pauza';
}

.playback-btn.primary.playing .btn-text {
    font-size: 0;
}

/* Speed Buttons */
.speed-buttons {
    display: flex;
    gap: 6px;
}

.speed-btn {
    flex: 1;
    padding: 10px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    background: var(--bg-tertiary);
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--text-secondary);
    cursor: pointer;
    transition: var(--transition);
}

.speed-btn.active {
    background: var(--text-primary);
    color: var(--bg-primary);
    border-color: var(--text-primary);
}

/* Toggle Options */
.toggle-option {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 0;
    cursor: pointer;
}

.toggle-option input {
    display: none;
}

.toggle-slider {
    width: 40px;
    height: 22px;
    background: var(--border-color);
    border-radius: 11px;
    position: relative;
    transition: var(--transition);
}

.toggle-slider::after {
    content: '';
    position: absolute;
    width: 18px;
    height: 18px;
    background: white;
    border-radius: 50%;
    top: 2px;
    left: 2px;
    transition: var(--transition);
}

.toggle-option input:checked+.toggle-slider {
    background: var(--accent-color);
}

.toggle-option input:checked+.toggle-slider::after {
    left: 20px;
}

.toggle-text {
    font-size: 0.8rem;
    color: var(--text-secondary);
}

/* Statistics */
.stats-section {
    background: var(--bg-tertiary);
    border-radius: 10px;
    padding: 15px;
    margin-top: auto;
}

.stat-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 6px 0;
    font-size: 0.8rem;
}

.stat-label {
    color: var(--text-secondary);
}

.stat-value {
    font-weight: 700;
    color: var(--text-primary);
    margin-left: auto;
}

.stat-unit {
    color: var(--text-secondary);
    font-size: 0.7rem;
}

.stat-item.ratio {
    border-top: 1px solid var(--border-color);
    margin-top: 8px;
    padding-top: 10px;
}

.stat-item.ratio .stat-value {
    color: var(--accent-color);
    font-size: 1rem;
}

/* ===== Simulation Container ===== */
.simulation-container {
    background: var(--bg-secondary);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.simulation-header {
    text-align: center;
    padding: 10px 15px;
    background: linear-gradient(135deg, rgba(52, 152, 219, 0.1), rgba(41, 128, 185, 0.1));
    border-radius: 10px;
    border-left: 4px solid #3498db;
}

.simulation-header h2 {
    font-size: 1.1rem;
    font-weight: 700;
    color: #3498db;
    margin-bottom: 6px;
}

.simulation-header p {
    font-size: 0.8rem;
    color: var(--text-secondary);
    line-height: 1.5;
    max-width: 600px;
    margin: 0 auto;
}

.simulation-wrapper {
    flex: 1;
    position: relative;
    background: linear-gradient(180deg, #1a3a52 0%, #2c5a7c 100%);
    border-radius: 12px;
    overflow: hidden;
    min-height: 450px;
    border: 3px solid var(--border-color);
}

#electrolysisCanvas {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
}

/* Electrode Labels */
.electrode-label {
    position: absolute;
    bottom: 15px;
    background: rgba(0, 0, 0, 0.7);
    padding: 8px 15px;
    border-radius: 20px;
    display: flex;
    align-items: center;
    gap: 8px;
    z-index: 10;
}

.cathode-label {
    left: 15%;
    transform: translateX(-50%);
}

.anode-label {
    right: 15%;
    transform: translateX(50%);
}

.electrode-sign {
    font-size: 1.5rem;
    font-weight: 800;
}

.cathode-label .electrode-sign {
    color: #5a6270;
}

.anode-label .electrode-sign {
    color: #e74c3c;
}

.electrode-name {
    color: white;
    font-size: 0.85rem;
    font-weight: 600;
}

/* Gas Collection Tubes */
.gas-tube {
    position: absolute;
    top: 10px;
    width: 50px;
    height: 120px;
    background: rgba(255, 255, 255, 0.15);
    border: 2px solid rgba(255, 255, 255, 0.3);
    border-radius: 5px 5px 0 0;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
}

#h2Tube {
    left: 15%;
    transform: translateX(-50%);
}

#o2Tube {
    right: 15%;
    transform: translateX(50%);
}

.gas-fill {
    width: 100%;
    background: rgba(255, 255, 255, 0.4);
    transition: height 0.5s ease;
}

#h2Fill {
    height: 0%;
    background: linear-gradient(180deg, rgba(236, 240, 241, 0.8), rgba(236, 240, 241, 0.4));
}

#o2Fill {
    height: 0%;
    background: linear-gradient(180deg, rgba(231, 76, 60, 0.6), rgba(231, 76, 60, 0.3));
}

.gas-label {
    position: absolute;
    top: -25px;
    left: 50%;
    transform: translateX(-50%);
    color: white;
    font-size: 0.9rem;
    font-weight: 700;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.5);
}

/* Equation Bar */
.equation-bar {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 15px;
    padding: 15px;
    background: var(--bg-tertiary);
    border-radius: 10px;
    font-size: 1.2rem;
    font-weight: 600;
}

.equation {
    color: var(--text-primary);
}

.arrow {
    color: var(--accent-color);
    font-size: 1.5rem;
}

.plus {
    color: var(--text-secondary);
}

/* ===== Info Panel ===== */
.info-panel {
    background: var(--bg-secondary);
    border-radius: var(--radius);
    padding: 20px;
    box-shadow: var(--shadow);
    display: flex;
    flex-direction: column;
    gap: 15px;
    overflow-y: auto;
}

.info-panel h2 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
}

.info-card {
    background: var(--bg-tertiary);
    border-radius: 10px;
    padding: 15px;
}

.info-card h3 {
    font-size: 0.9rem;
    margin-bottom: 8px;
}

.info-card p {
    font-size: 0.8rem;
    color: var(--text-secondary);
    line-height: 1.5;
}

.info-card ul {
    list-style: none;
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.info-card ul li {
    padding: 4px 0;
    position: relative;
    padding-left: 15px;
}

.info-card ul li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--accent-color);
}

.info-card.highlight {
    background: linear-gradient(135deg, rgba(52, 152, 219, 0.15), rgba(41, 128, 185, 0.1));
    border-left: 4px solid var(--accent-color);
}

/* Reactions Card */
.reactions-card {
    background: var(--bg-tertiary);
    border-radius: 10px;
    padding: 15px;
}

.reactions-card h3 {
    font-size: 0.9rem;
    margin-bottom: 12px;
}

.reaction {
    display: flex;
    flex-direction: column;
    gap: 3px;
    padding: 8px 0;
    border-bottom: 1px solid var(--border-color);
}

.reaction:last-child {
    border-bottom: none;
}

.reaction-label {
    font-size: 0.7rem;
    color: var(--text-secondary);
    text-transform: uppercase;
}

.reaction-eq {
    font-size: 0.85rem;
    font-weight: 600;
    font-family: 'Courier New', monospace;
}

/* Legend Card */
.legend-card {
    background: var(--bg-tertiary);
    border-radius: 10px;
    padding: 15px;
}

.legend-card h3 {
    font-size: 0.9rem;
    margin-bottom: 10px;
}

.legend-items {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.legend-dot {
    width: 16px;
    height: 16px;
    border-radius: 50%;
    border: 2px solid rgba(0, 0, 0, 0.2);
}

.legend-dot.oxygen {
    background: #e74c3c;
}

.legend-dot.hydrogen {
    background: #ecf0f1;
}

.legend-dot.electron {
    background: #f1c40f;
}

/* ===== Responsive ===== */
@media (max-width: 1200px) {
    .main-content {
        grid-template-columns: 200px 1fr 240px;
    }
}

@media (max-width: 900px) {
    .main-content {
        grid-template-columns: 1fr;
    }

    .controls-panel {
        order: 1;
    }

    .simulation-container {
        order: 2;
        min-height: 400px;
    }

    .info-panel {
        order: 3;
    }
}