/* Base Variables - Premium Aesthetics */
:root {
    /* Typgraphy */
    --font-primary: 'Inter', system-ui, -apple-system, sans-serif;

    /* Animation Tokens */
    --transition-fast: 0.15s ease-out;
    --transition-medium: 0.3s cubic-bezier(0.4, 0, 0.2, 1);

    /* Layout */
    --max-width: 1200px;
    --border-radius: 12px;
    --border-radius-sm: 8px;
    --spacing-1: 0.25rem;
    --spacing-2: 0.5rem;
    --spacing-3: 1rem;
    --spacing-4: 1.5rem;
    --spacing-5: 2rem;
    --spacing-6: 3rem;
}

/* Light Theme Variables */
.theme-light {
    --bg-app: #f8fafc;
    --bg-surface: #ffffff;
    --bg-surface-elevated: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --border-color: #e2e8f0;

    --accent-primary: #3b82f6;
    --accent-hover: #2563eb;

    --success: #22c55e;
    --warning: #f59e0b;
    --danger: #ef4444;

    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
}

/* Dark Theme Variables (Default) */
.theme-dark {
    --bg-app: #09090b;
    --bg-surface: #18181b;
    --bg-surface-elevated: #27272a;
    --text-primary: #f8fafc;
    --text-secondary: #a1a1aa;
    --border-color: #3f3f46;

    --accent-primary: #60a5fa;
    --accent-hover: #3b82f6;

    --success: #4ade80;
    --warning: #fbbf24;
    --danger: #f87171;

    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.5);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.4), 0 2px 4px -2px rgb(0 0 0 / 0.4);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.5), 0 4px 6px -4px rgb(0 0 0 / 0.5);
}

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

body {
    font-family: var(--font-primary);
    background-color: var(--bg-app);
    color: var(--text-primary);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
    transition: background-color var(--transition-medium), color var(--transition-medium);
}

#app {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

/* Header & Navigation */
.navbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--spacing-3) var(--spacing-5);
    background-color: var(--bg-surface);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 10;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-2);
}

.logo-icon {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent-primary);
}

.logo h1 {
    font-size: 1.25rem;
    font-weight: 600;
    letter-spacing: -0.025em;
}

.nav-links {
    display: flex;
    gap: var(--spacing-4);
}

.nav-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    font-family: var(--font-primary);
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    padding: var(--spacing-2) var(--spacing-1);
    position: relative;
    transition: color var(--transition-fast);
}

.nav-btn:hover {
    color: var(--text-primary);
}

.nav-btn.active {
    color: var(--accent-primary);
}

.nav-btn.active::after {
    content: '';
    position: absolute;
    bottom: -0.5rem;
    left: 0;
    right: 0;
    height: 2px;
    background-color: var(--accent-primary);
    border-radius: 2px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.6rem 1.2rem;
    border-radius: var(--border-radius-sm);
    font-family: var(--font-primary);
    font-weight: 500;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all var(--transition-fast);
    border: none;
}

.btn.primary {
    background-color: var(--accent-primary);
    color: #fff;
    box-shadow: var(--shadow-sm);
}

.theme-dark .btn.primary {
    color: #000;
}

.btn.primary:hover {
    background-color: var(--accent-hover);
    transform: translateY(-1px);
}

.btn.secondary {
    background-color: var(--bg-surface-elevated);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

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

.btn.danger {
    background-color: rgba(239, 68, 68, 0.1);
    color: var(--danger);
    border: 1px solid rgba(239, 68, 68, 0.3);
}

.btn.danger:hover {
    background-color: var(--danger);
    color: #fff;
}

.icon-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: var(--spacing-2);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color var(--transition-fast), color var(--transition-fast);
}

.icon-btn:hover {
    background-color: var(--bg-surface-elevated);
    color: var(--text-primary);
}

/* Main Content Area */
.content-area {
    flex: 1;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: var(--spacing-4) var(--spacing-4);
    width: 100%;
}

.view {
    display: none;
    animation: fadeIn var(--transition-medium);
}

.view.active {
    display: block;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.view-header {
    text-align: center;
    margin-bottom: var(--spacing-4);
}

.view-header h2 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: var(--spacing-2);
    letter-spacing: -0.025em;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

/* Utilities */
.hidden {
    display: none !important;
}

.card {
    background-color: var(--bg-surface);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: var(--spacing-4);
    box-shadow: var(--shadow-sm);
}

/* Grid Specifics (Placeholders for JS) */
.grid-controls {
    display: flex;
    justify-content: center;
    gap: var(--spacing-4);
    margin-bottom: var(--spacing-4);
    align-items: center;
}

.grid-wrapper {
    overflow: auto;
    padding-bottom: var(--spacing-4);
    max-height: 80vh;
}

/* Sticky header row */
.practice-grid tr:first-child th {
    position: sticky;
    top: 0;
    z-index: 2;
}

/* Sticky first column */
.practice-grid th:first-child {
    position: sticky;
    left: 0;
    z-index: 1;
}

/* Corner cell stays above both axes */
.practice-grid tr:first-child th:first-child {
    z-index: 3;
}

/* Flashcards Specifics */
.session-stats {
    display: flex;
    justify-content: center;
    gap: var(--spacing-4);
    margin-bottom: var(--spacing-4);
}

.stat-pill {
    background-color: var(--bg-surface-elevated);
    border: 1px solid var(--border-color);
    padding: 0.25rem 0.75rem;
    border-radius: 999px;
    font-size: 0.875rem;
    font-weight: 500;
}

.card-area {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 300px;
}

.empty-state {
    text-align: center;
    color: var(--text-secondary);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-3);
}

/* Number Toggles */
.toggles-container {
    text-align: center;
    margin-bottom: var(--spacing-4);
}

.toggles-label {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-2);
}

.number-toggles {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    justify-content: center;
}

.toggle-btn {
    width: 2.5rem;
    height: 2.5rem;
    border-radius: 50%;
    border: 2px solid var(--border-color);
    background-color: var(--bg-surface-elevated);
    color: var(--text-primary);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    justify-content: center;
}

.toggle-btn.active {
    border-color: var(--text-primary);
    transform: scale(1.1);
    box-shadow: 0 0 0 2px var(--bg-app), 0 0 0 4px var(--text-primary);
}

/* Report View Specifics */
.dashboard-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-4);
}

.stat-card h3 {
    font-size: 0.9rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: var(--spacing-2);
}

.stat-value {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

.heatmap-card.full-width {
    grid-column: 1 / -1;
}

.heatmap-wrapper {
    margin-top: var(--spacing-4);
    /* JS will populate this */
}

.heatmap-legend {
    display: flex;
    align-items: center;
    gap: var(--spacing-2);
    margin-top: var(--spacing-4);
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.legend-item {
    width: 16px;
    height: 16px;
    border-radius: 4px;
}

/* Helper colors for heatmap */
.bg-red-500 {
    background-color: var(--danger);
}

.bg-orange-500 {
    background-color: var(--warning);
}

.bg-yellow-500 {
    background-color: #fde047;
}

.bg-green-500 {
    background-color: var(--success);
}

/* Forms & Selects */
select,
input {
    background-color: var(--bg-surface-elevated);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
    padding: 0.5rem;
    border-radius: var(--border-radius-sm);
    font-family: inherit;
    font-size: 0.95rem;
}

select:focus,
input:focus {
    outline: 2px solid var(--accent-primary);
    outline-offset: -1px;
}

/* Modal */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background-color: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 50;
    opacity: 1;
    transition: opacity var(--transition-medium);
}

.modal.hidden {
    opacity: 0;
    pointer-events: none;
}

.modal-content {
    background-color: var(--bg-surface);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    width: 90%;
    max-width: 400px;
    box-shadow: var(--shadow-lg);
    overflow: hidden;
    transform: scale(1);
    transition: transform var(--transition-medium);
}

.modal.hidden .modal-content {
    transform: scale(0.95);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-4);
    border-bottom: 1px solid var(--border-color);
}

.modal-body {
    padding: var(--spacing-4);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-4);
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-1);
}

.form-group label {
    font-weight: 500;
    font-size: 0.9rem;
}

hr {
    border: none;
    border-top: 1px solid var(--border-color);
}

.danger-zone p {
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-2);
}

/* Footer */
.app-footer {
    text-align: center;
    padding: var(--spacing-2) var(--spacing-3);
    font-size: 0.8rem;
    color: var(--text-secondary);
    border-top: 1px solid var(--border-color);
}

.app-footer a {
    color: var(--accent-primary);
    text-decoration: none;
}

.app-footer a:hover {
    text-decoration: underline;
}

/* Responsiveness */
@media (max-width: 768px) {
    .navbar {
        flex-direction: column;
        gap: var(--spacing-3);
        padding: var(--spacing-3);
    }

    .nav-links {
        width: 100%;
        justify-content: space-around;
    }

    .actions {
        position: absolute;
        top: var(--spacing-3);
        right: var(--spacing-3);
    }

    .view-header h2 {
        font-size: 1.5rem;
    }

    /* Lock grid view to viewport so sticky headers stay visible */
    #app {
        height: 100dvh;
        overflow: hidden;
    }

    .content-area {
        display: flex;
        flex-direction: column;
        overflow: hidden;
        min-height: 0;
    }

    .view.active {
        flex: 1;
        overflow: auto;
        min-height: 0;
    }

    #view-grid.active {
        display: flex;
        flex-direction: column;
        overflow: auto;
    }

    #view-grid .view-header,
    #view-grid .grid-controls {
        flex-shrink: 0;
    }

    #view-grid .grid-wrapper {
        flex: none;
        height: calc(100% - 4rem);
        max-height: none;
        min-height: 0;
    }

    .app-footer {
        flex-shrink: 0;
    }
}

/* Chrome, Safari, Edge, Opera */
input::-webkit-outer-spin-button,
input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

/* Firefox */
input[type=number] {
  -moz-appearance: textfield;
}