/* === Base === */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --bg-dark:     #0f0f1a;
    --bg-panel:    #161628;
    --bg-card:     #1c1c36;
    --border:      #2a2a4a;
    --text:        #e0e0e0;
    --text-dim:    rgba(255,255,255,0.5);
    --accent:      #00ff88;
    --accent-blue: #00ccff;
    --warn:        #f1c40f;
    --danger:      #e74c3c;
}

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    background: var(--bg-dark);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* === Header === */
header {
    background: linear-gradient(135deg, #0a1628, #162040);
    padding: 14px 24px;
    display: flex;
    align-items: baseline;
    gap: 16px;
    border-bottom: 1px solid var(--border);
}

header h1 {
    font-size: 20px;
    font-weight: 600;
    letter-spacing: 0.5px;
}

.header-subtitle {
    font-size: 12px;
    color: var(--text-dim);
    letter-spacing: 1px;
    text-transform: uppercase;
}

/* === Setup Bar === */
#setup-bar {
    background: var(--bg-panel);
    border-bottom: 1px solid var(--border);
    padding: 12px 24px;
    display: flex;
    flex-wrap: wrap;
    align-items: flex-end;
    gap: 16px;
}

.setup-group {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.setup-group label {
    font-size: 10px;
    text-transform: uppercase;
    letter-spacing: 0.8px;
    color: var(--text-dim);
}

.setup-group input,
.setup-group select {
    background: var(--bg-dark);
    border: 1px solid var(--border);
    border-radius: 4px;
    color: var(--text);
    padding: 6px 10px;
    font-size: 13px;
    font-family: monospace;
    width: 100px;
}

.setup-group select {
    width: 220px;
}

.setup-group select#turn-direction {
    width: 100px;
}

.setup-group input:focus,
.setup-group select:focus {
    outline: none;
    border-color: var(--accent-blue);
}

.setup-actions {
    display: flex;
    gap: 8px;
    margin-left: auto;
}

button {
    background: var(--accent-blue);
    color: #000;
    border: none;
    border-radius: 4px;
    padding: 8px 16px;
    font-size: 13px;
    font-weight: 600;
    cursor: pointer;
    transition: opacity 0.15s;
}

button:hover {
    opacity: 0.85;
}

button:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

.btn-secondary {
    background: transparent;
    border: 1px solid var(--border);
    color: var(--text-dim);
}

.btn-secondary:hover {
    border-color: var(--text-dim);
    color: var(--text);
}

/* === Main Content === */
#main-content {
    flex: 1;
    display: flex;
    min-height: 0;
    overflow: hidden;
}

/* === Sidebar === */
#sim-sidebar {
    width: 400px;
    min-width: 400px;
    background: var(--bg-panel);
    border-right: 1px solid var(--border);
    overflow-y: auto;
    padding: 12px;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

#sidebar-placeholder {
    padding: 40px 20px;
    text-align: center;
    color: var(--text-dim);
}

#sidebar-placeholder .hint {
    font-size: 12px;
    margin-top: 8px;
}

/* === Simulation Card === */
.sim-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-left: 3px solid #fff;
    border-radius: 6px;
    padding: 10px 12px;
}

.sim-card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 8px;
}

.sim-card-title {
    font-size: 13px;
    font-weight: 600;
}

.sim-remove-btn {
    background: transparent;
    border: none;
    color: var(--text-dim);
    font-size: 18px;
    padding: 0 4px;
    cursor: pointer;
    line-height: 1;
}

.sim-remove-btn:hover {
    color: var(--danger);
}

.sim-replay-btn {
    background: transparent;
    border: none;
    color: var(--accent-blue);
    font-size: 16px;
    padding: 0 4px;
    cursor: pointer;
    line-height: 1;
}

.sim-replay-btn:hover {
    color: var(--accent);
}

/* === Gauges === */
.gauge-row {
    display: flex;
    justify-content: center;
    gap: 8px;
}

.gauge-wrap {
    display: flex;
    align-items: center;
    justify-content: center;
}

.gauge-wrap canvas {
    display: block;
}

/* === Parameter Chain === */
.param-chain {
    margin-top: 8px;
    padding: 6px 8px;
    background: rgba(0,0,0,0.25);
    border-radius: 4px;
    font-family: monospace;
    font-size: 10px;
    color: var(--text-dim);
    line-height: 1.6;
    word-break: break-word;
}

.chain-label {
    color: var(--accent-blue);
}

.chain-arrow {
    color: var(--text-dim);
    margin: 0 2px;
}

.chain-warn {
    color: var(--danger);
    font-weight: bold;
    margin-left: 4px;
}

/* === Canvas Area === */
#canvas-area {
    flex: 1;
    min-width: 0;
    display: flex;
    align-items: stretch;
    justify-content: stretch;
    padding: 12px;
}

#simulation-canvas {
    width: 100%;
    height: 100%;
    background: var(--bg-dark);
    border: 1px solid var(--border);
    border-radius: 6px;
}

/* === Explainer Panel === */
#explainer-section {
    border-top: 1px solid var(--border);
    background: var(--bg-panel);
}

#explainer-toggle {
    width: 100%;
    text-align: left;
    padding: 10px 24px;
    border-radius: 0;
    font-size: 13px;
    letter-spacing: 0.5px;
}

#explainer-content {
    max-height: 600px;
    overflow-y: auto;
    padding: 0 24px 16px;
    transition: max-height 0.3s ease, padding 0.3s ease;
}

#explainer-content.collapsed {
    max-height: 0;
    padding-top: 0;
    padding-bottom: 0;
    overflow: hidden;
}

.explainer-block {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-left: 3px solid #fff;
    border-radius: 6px;
    padding: 12px;
    margin-top: 12px;
}

.explainer-block-title {
    font-size: 13px;
    font-weight: 600;
    margin-bottom: 10px;
}

.explainer-row {
    display: flex;
    align-items: baseline;
    gap: 12px;
    padding: 3px 0;
    font-family: monospace;
    font-size: 11px;
    border-bottom: 1px solid rgba(255,255,255,0.04);
}

.explainer-label {
    color: var(--accent-blue);
    min-width: 160px;
    flex-shrink: 0;
}

.explainer-formula {
    color: var(--text-dim);
    min-width: 220px;
    flex-shrink: 0;
}

.explainer-value {
    flex: 1;
}

.explainer-result {
    color: var(--accent);
    font-weight: 600;
}

/* === Responsive === */
@media (max-width: 900px) {
    #main-content {
        flex-direction: column;
    }

    #sim-sidebar {
        width: 100%;
        min-width: 0;
        max-height: 300px;
        border-right: none;
        border-bottom: 1px solid var(--border);
    }

    #canvas-area {
        min-height: 400px;
    }
}