:root {
    --primary: #6366f1;
    --primary-hover: #4f46e5;
    --bg-dark: #0f172a;
    --sidebar-bg: #1e293b;
    --text-main: #f8fafc;
    --text-dim: #94a3b8;
    --border-color: #334155;
    --glass-bg: rgba(255, 255, 255, 0.1);
    --glass-border: rgba(255, 255, 255, 0.2);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, sans-serif;
}

body {
    background-color: #000;
    color: var(--text-main);
    overflow: hidden;
    height: 100vh;
}

.app-container {
    display: flex;
    height: 100vh;
}

/* Sidebar Styling */
.sidebar {
    width: 380px;
    background: var(--sidebar-bg);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    z-index: 10;
    box-shadow: 10px 0 30px rgba(0, 0, 0, 0.3);
}

.sidebar header {
    padding: 2rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.sidebar h1 {
    font-size: 1.5rem;
    font-weight: 800;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--primary);
}

.sidebar header p {
    color: var(--text-dim);
    font-size: 0.875rem;
    margin-top: 0.25rem;
}

.tabs {
    display: flex;
    padding: 0.75rem;
    gap: 0.5rem;
    background: rgba(0, 0, 0, 0.1);
}

.tab-btn {
    flex: 1;
    padding: 0.75rem;
    border: none;
    background: transparent;
    color: var(--text-dim);
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 600;
    transition: var(--transition);
}

.tab-btn.active {
    background: var(--primary);
    color: white;
}

.tab-content {
    display: none;
    padding: 1.5rem;
    flex: 1;
    overflow-y: auto;
}

.tab-content.active {
    display: block;
}

/* Controls Styling */
.control-group {
    margin-bottom: 2rem;
}

.control-group label {
    display: block;
    font-size: 0.875rem;
    font-weight: 700;
    margin-bottom: 0.75rem;
    color: var(--text-dim);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.row {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 0.75rem;
}

.input-field {
    flex: 1;
    background: rgba(0, 0, 0, 0.2);
    padding: 0.5rem 0.75rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 0.5rem;
}

.input-field span {
    font-size: 0.75rem;
    color: var(--text-dim);
    white-space: nowrap;
}

.slider-field {
    margin-top: 1rem;
}

.slider-field span {
    display: block;
    font-size: 0.75rem;
    color: var(--text-dim);
    margin-bottom: 0.5rem;
}

.slider-field input[type="range"] {
    width: 100%;
    accent-color: var(--primary);
    cursor: pointer;
}

input[type="number"],
input[type="text"],
select {
    background: transparent;
    border: none;
    color: white;
    width: 100%;
    outline: none;
    padding: 4px 0;
}

input[type="color"] {
    width: 44px;
    height: 44px;
    border: none;
    border-radius: 8px;
    background: transparent;
    cursor: pointer;
}

.primary-btn,
.save-btn {
    width: 100%;
    padding: 0.875rem;
    border: none;
    border-radius: 12px;
    font-weight: 700;
    cursor: pointer;
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.primary-btn {
    background: rgba(99, 102, 241, 0.1);
    color: var(--primary);
    border: 1px solid var(--primary);
}

.primary-btn:hover {
    background: var(--primary);
    color: white;
}

.save-btn {
    background: var(--primary);
    color: white;
    font-size: 1rem;
}

.save-btn:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 10px 20px rgba(99, 102, 241, 0.3);
}

.secondary-btn {
    padding: 0.875rem;
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-dim);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    cursor: pointer;
    transition: var(--transition);
}

.secondary-btn:hover {
    background: rgba(255, 255, 255, 0.1);
    color: white;
}

/* Subject Pool */
.subject-pool {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
    max-height: 350px;
    overflow-y: auto;
    padding: 0.5rem;
    background: rgba(0, 0, 0, 0.2);
    border-radius: 12px;
}

.pool-item {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--border-color);
    padding: 0.8rem 1rem;
    border-radius: 12px;
    cursor: grab;
    transition: var(--transition);
    position: relative;
    user-select: none;
}

.pool-item:hover {
    border-color: var(--primary);
    background: rgba(99, 102, 241, 0.1);
}

.pool-item:active {
    cursor: grabbing;
}

.pool-item .color-tag {
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 6px;
    height: 70%;
    border-radius: 0 4px 4px 0;
}

.pool-item-info {
    padding-left: 0.75rem;
}

.pool-item h4 {
    font-size: 0.95rem;
    font-weight: 700;
}

.pool-item p {
    font-size: 0.75rem;
    color: var(--text-dim);
    margin-top: 2px;
}

.delete-pool-item {
    position: absolute;
    right: 1rem;
    top: 50%;
    transform: translateY(-50%);
    color: #ef4444;
    opacity: 0.4;
    transition: var(--transition);
    padding: 5px;
}

.delete-pool-item:hover {
    opacity: 1;
    transform: translateY(-50%) scale(1.1);
}

/* Preview Area */
.preview-area {
    flex: 1;
    background: #000;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 2rem;
    position: relative;
}

.canvas-container {
    background: #111;
    padding: 10px;
    border-radius: 20px;
    box-shadow: 0 50px 100px rgba(0, 0, 0, 0.5);
    transform: scale(0.6);
    transform-origin: center;
}

.wallpaper-preview {
    width: 1179px;
    height: 2556px;
    background: var(--bg-dark);
    position: relative;
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
}

.timetable-card {
    width: 90%;
    max-width: 1024px;
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: 24px;
    padding: 30px;
    display: grid;
    /* Grid template handled via JS */
}

/* Grid Items */
.grid-header {
    font-weight: 800;
    color: rgba(255, 255, 255, 0.8);
    text-align: center;
    padding: 15px;
    font-size: 24px;
}

.time-label {
    grid-column: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 18px;
    color: rgba(255, 255, 255, 0.5);
    border-right: 1px solid rgba(255, 255, 255, 0.1);
}

.grid-slot {
    border-right: 1px solid rgba(255, 255, 255, 0.03);
    border-bottom: 1px solid rgba(255, 255, 255, 0.03);
    transition: background 0.2s ease;
}

.grid-slot.drag-over {
    background: rgba(99, 102, 241, 0.25) !important;
}

/* Disable subject items during drag to allow dropping "through" them */
.app-container.is-dragging .subject-item {
    pointer-events: none;
    opacity: 0.8;
}

.subject-item {
    position: relative;
    border-radius: 12px;
    margin: 4px;
    padding: 12px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    font-weight: 700;
    color: white;
    cursor: pointer;
    transition: var(--transition);
    overflow: hidden;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
    border: 1px solid rgba(255, 255, 255, 0.15);
    max-height: calc(100% - 8px);
    /* Ensure it doesn't push the row */
}

.subject-item:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.4);
    z-index: 10;
}

.subject-item .name {
    font-size: 1.1rem;
    line-height: 1.2;
    margin-bottom: 4px;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.subject-item .details {
    font-size: 0.8rem;
    opacity: 0.9;
    font-weight: 400;
}

/* Action Overlay */
.subject-actions {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(4px);
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 15px;
    opacity: 0;
    transition: var(--transition);
}

.subject-item:hover .subject-actions {
    opacity: 1;
}

.action-btn {
    width: 38px;
    height: 38px;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    background: white;
    color: #111;
    cursor: pointer;
    transition: var(--transition);
}

.action-btn:hover {
    transform: scale(1.15);
}

.action-btn.delete {
    color: #ef4444;
}

.help-text {
    font-size: 0.75rem;
    color: var(--text-dim);
    margin-top: 0.5rem;
    line-height: 1.4;
}

.hidden {
    display: none;
}

.preview-info {
    position: absolute;
    bottom: 2rem;
    color: var(--text-dim);
    font-size: 0.9rem;
    text-align: center;
    padding: 0 1rem;
}

/* Mobile Responsiveness */
@media (max-width: 850px) {
    .app-container {
        flex-direction: column;
        overflow-y: auto;
    }

    .sidebar {
        width: 100%;
        height: auto;
        min-height: auto;
        border-right: none;
        border-bottom: 1px solid var(--border-color);
        box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
    }

    .sidebar header {
        padding: 1.5rem 1rem;
    }

    .tab-content {
        max-height: 400px;
        padding: 1rem;
    }

    .preview-area {
        padding: 3rem 1rem;
        min-height: 600px;
    }

    .canvas-container {
        transform: scale(0.4) !important;
        /* Smaller scale for mobile */
    }

    .preview-info {
        position: relative;
        bottom: 0;
        margin-top: 1rem;
        margin-bottom: 2rem;
    }

    /* Adjust subject pool for mobile */
    .subject-pool {
        flex-direction: row;
        overflow-x: auto;
        overflow-y: hidden;
        max-height: none;
        padding-bottom: 10px;
    }

    .pool-item {
        flex: 0 0 160px;
        padding: 0.6rem;
    }

    .pool-item .color-tag {
        width: 100%;
        height: 6px;
        top: 0;
        left: 0;
        transform: none;
        border-radius: 4px 4px 0 0;
    }

    .pool-item-info {
        padding-left: 0;
        margin-top: 8px;
    }

    /* Mobile active selection indicator */
    .pool-item.selected {
        border-color: var(--primary);
        background: rgba(99, 102, 241, 0.2);
        box-shadow: 0 0 15px rgba(99, 102, 241, 0.4);
    }
}