/* CSS Custom Properties */
:root {
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --accent: #3b82f6;
    --accent-hover: #2563eb;

    /* Class type colors */
    --type-P: #3b82f6; /* Lecture - blue */
    --type-P-bg: #dbeafe;
    --type-S: #eab308; /* Seminar - yellow */
    --type-S-bg: #fef9c3;
    --type-C: #22c55e; /* Exercise - green */
    --type-C-bg: #dcfce7;

    /* Grid settings */
    --time-col-width: 60px;

    --shadow: 0 1px 3px rgba(0,0,0,0.1);
    --radius: 8px;
}

/* Dark theme */
[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --border-color: #475569;

    --type-P-bg: #1e3a5f;
    --type-S-bg: #422006;
    --type-C-bg: #14532d;
}

@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
        --bg-primary: #0f172a;
        --bg-secondary: #1e293b;
        --bg-tertiary: #334155;
        --text-primary: #f1f5f9;
        --text-secondary: #94a3b8;
        --border-color: #475569;

        --type-P-bg: #1e3a5f;
        --type-S-bg: #422006;
        --type-C-bg: #14532d;
    }
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.5;
    min-height: 100vh;
}

/* Header */
header {
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

header h1 {
    font-size: 1.5rem;
    font-weight: 600;
}

.controls {
    display: flex;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
}

.control-group {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.control-group label {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

select {
    padding: 0.5rem 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    background: var(--bg-primary);
    color: var(--text-primary);
    font-size: 0.875rem;
    cursor: pointer;
}

select:focus {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

#theme-toggle {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 0.5rem;
    cursor: pointer;
    font-size: 1.25rem;
    line-height: 1;
}

#theme-toggle .icon-dark {
    display: none;
}

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

[data-theme="dark"] #theme-toggle .icon-dark {
    display: inline;
}

@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) #theme-toggle .icon-light {
        display: none;
    }
    :root:not([data-theme="light"]) #theme-toggle .icon-dark {
        display: inline;
    }
}

/* Main layout */
main {
    display: grid;
    grid-template-columns: 1fr 280px;
    gap: 1.5rem;
    padding: 1.5rem;
    max-width: 1600px;
    margin: 0 auto;
}

@media (max-width: 1024px) {
    main {
        grid-template-columns: 1fr;
    }

    .stats-panel {
        order: -1;
    }
}

/* Timetable Grid */
.timetable-container {
    overflow-x: auto;
}

.timetable-grid {
    display: grid;
    grid-template-columns: var(--time-col-width) repeat(5, 1fr);
    min-width: 700px;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
}

.grid-header {
    background: var(--bg-tertiary);
    padding: 0.75rem 0.5rem;
    text-align: center;
    font-weight: 600;
    font-size: 0.875rem;
    border-bottom: 1px solid var(--border-color);
    border-right: 1px solid var(--border-color);
}

.grid-header:last-of-type {
    border-right: none;
}

/* Time column */
.time-column {
    position: relative;
    background: var(--bg-tertiary);
    border-right: 1px solid var(--border-color);
}

.time-label {
    position: absolute;
    right: 0.5rem;
    font-size: 0.75rem;
    color: var(--text-secondary);
    transform: translateY(-50%);
}

/* Day columns */
.day-column {
    position: relative;
    border-right: 1px solid var(--border-color);
}

.day-column:last-child {
    border-right: none;
}

/* Hour lines */
.hour-line {
    position: absolute;
    left: 0;
    right: 0;
    height: 1px;
    background: var(--border-color);
}

/* Class blocks */
.class-block {
    position: absolute;
    left: 2px;
    right: 2px;
    border-radius: 4px;
    padding: 4px 6px;
    font-size: 0.75rem;
    overflow: hidden;
    cursor: pointer;
    transition: transform 0.15s ease, box-shadow 0.15s ease;
    border-left: 3px solid;
    z-index: 1;
}

.class-block:hover {
    transform: scale(1.02);
    box-shadow: var(--shadow);
    z-index: 10;
}

.class-block.type-P {
    background: var(--type-P-bg);
    border-left-color: var(--type-P);
}

.class-block.type-S {
    background: var(--type-S-bg);
    border-left-color: var(--type-S);
}

.class-block.type-C {
    background: var(--type-C-bg);
    border-left-color: var(--type-C);
}

.class-name {
    font-weight: 600;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.class-time {
    color: var(--text-secondary);
    font-size: 0.65rem;
}

.class-room {
    color: var(--text-secondary);
    font-size: 0.65rem;
}

/* Stats Panel */
.stats-panel {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 1.25rem;
    height: fit-content;
    position: sticky;
    top: 1.5rem;
}

.stats-panel h2 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 1rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border-color);
}

.stat-item {
    display: flex;
    justify-content: space-between;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border-color);
}

.stat-item:last-child {
    border-bottom: none;
}

.stat-label {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.stat-value {
    font-weight: 600;
    font-size: 0.875rem;
}

.stat-score {
    margin-top: 0.5rem;
    padding-top: 0.75rem;
    border-top: 2px solid var(--border-color);
}

.stat-score .stat-value {
    color: var(--accent);
    font-size: 1.25rem;
}

/* Legend */
.legend {
    display: flex;
    justify-content: center;
    gap: 1.5rem;
    padding: 1rem;
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    flex-wrap: wrap;
}

.legend-item {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.legend-color {
    width: 16px;
    height: 16px;
    border-radius: 4px;
    border-left: 3px solid;
}

.legend-color.type-P {
    background: var(--type-P-bg);
    border-left-color: var(--type-P);
}

.legend-color.type-S {
    background: var(--type-S-bg);
    border-left-color: var(--type-S);
}

.legend-color.type-C {
    background: var(--type-C-bg);
    border-left-color: var(--type-C);
}

/* Loading state */
.loading {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 3rem;
    color: var(--text-secondary);
}

.loading::after {
    content: '';
    width: 24px;
    height: 24px;
    border: 2px solid var(--border-color);
    border-top-color: var(--accent);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
    margin-left: 0.75rem;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Error state */
.error {
    background: #fef2f2;
    border: 1px solid #fecaca;
    color: #dc2626;
    padding: 1rem;
    border-radius: var(--radius);
    text-align: center;
}

[data-theme="dark"] .error {
    background: #450a0a;
    border-color: #7f1d1d;
    color: #fca5a5;
}

/* Mobile adjustments */
@media (max-width: 640px) {
    header {
        padding: 1rem;
    }

    header h1 {
        width: 100%;
        text-align: center;
    }

    .controls {
        width: 100%;
        justify-content: center;
    }

    main {
        padding: 1rem;
    }

    .timetable-grid {
        font-size: 0.75rem;
    }

    .class-block {
        padding: 2px 4px;
        font-size: 0.65rem;
    }
}