:root {
    --bg: #f8f9fa;
    --card-bg: #ffffff;
    --text: #2d3436;
    --text-secondary: #636e72;
    --border: #e0e4e8;
    --accent: #6c5ce7;
    --accent-light: #a29bfe;
    --success: #00b894;
    --danger: #e17055;
    --warning: #fdcb6e;
    --streak-bg: #fff3e0;
    --habit-1: #6c5ce7;
    --habit-2: #00b894;
    --habit-3: #e17055;
    --habit-4: #0984e3;
    --habit-5: #fdcb6e;
    --habit-6: #e84393;
    --habit-7: #00cec9;
    --habit-8: #6ab04c;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06), 0 1px 2px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08), 0 2px 4px rgba(0, 0, 0, 0.04);
    --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.12), 0 4px 8px rgba(0, 0, 0, 0.06);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
    --transition: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.dark {
    --bg: #1a1a2e;
    --card-bg: #222244;
    --text: #e0e0e0;
    --text-secondary: #a0a0b8;
    --border: #2e2e52;
    --streak-bg: #2a1f3d;
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.35);
    --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.45);
}

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

body {
    font-family: 'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
    background-color: var(--bg);
    color: var(--text);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    padding: 24px 16px 60px;
    transition: background-color 0.3s ease, color 0.3s ease;
    line-height: 1.5;
}

.container {
    width: 100%;
    max-width: 680px;
}

/* Header */
.header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 28px;
    flex-wrap: wrap;
    gap: 12px;
}

.header-left {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-icon {
    width: 42px;
    height: 42px;
    background: linear-gradient(135deg, var(--accent), var(--accent-light));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 22px;
    color: #fff;
    box-shadow: 0 4px 10px rgba(108, 92, 231, 0.3);
}

.header-title h1 {
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: -0.3px;
    line-height: 1.2;
}

.header-title .date-display {
    font-size: 0.85rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.header-actions {
    display: flex;
    gap: 8px;
    align-items: center;
}

/* Buttons */
.btn {
    padding: 10px 18px;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-weight: 600;
    font-size: 0.9rem;
    font-family: inherit;
    transition: all var(--transition);
    display: flex;
    align-items: center;
    gap: 6px;
    white-space: nowrap;
}

.btn-primary {
    background: var(--accent);
    color: #fff;
    box-shadow: 0 2px 8px rgba(108, 92, 231, 0.3);
}
.btn-primary:hover {
    background: #5a4bd1;
    box-shadow: 0 4px 14px rgba(108, 92, 231, 0.4);
    transform: translateY(-1px);
}

.btn-outline {
    background: transparent;
    color: var(--text);
    border: 2px solid var(--border);
}
.btn-outline:hover {
    border-color: var(--accent);
    color: var(--accent);
    background: rgba(108, 92, 231, 0.05);
}

.btn-icon {
    width: 38px;
    height: 38px;
    padding: 0;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    background: var(--card-bg);
    border: 2px solid var(--border);
    color: var(--text);
    cursor: pointer;
    transition: all var(--transition);
}
.btn-icon:hover {
    border-color: var(--accent);
    color: var(--accent);
    box-shadow: var(--shadow-md);
}

.btn-sm {
    padding: 6px 12px;
    font-size: 0.78rem;
    border-radius: 6px;
}

.btn-danger-sm {
    background: transparent;
    border: 1.5px solid var(--danger);
    color: var(--danger);
    padding: 6px 12px;
    font-size: 0.78rem;
    border-radius: 6px;
    cursor: pointer;
    font-weight: 600;
    font-family: inherit;
    transition: all var(--transition);
}
.btn-danger-sm:hover {
    background: var(--danger);
    color: #fff;
}

/* Stats Cards */
.stats-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: 14px;
    margin-bottom: 24px;
}

.stat-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    padding: 18px 16px;
    box-shadow: var(--shadow-sm);
    text-align: center;
    border: 1px solid var(--border);
    transition: all var(--transition);
    position: relative;
    overflow: hidden;
}
.stat-card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}
.stat-card .stat-value {
    font-size: 2rem;
    font-weight: 800;
    letter-spacing: -1px;
    line-height: 1;
    margin-bottom: 4px;
}
.stat-card .stat-label {
    font-size: 0.78rem;
    color: var(--text-secondary);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}
.stat-card.accent .stat-value {
    color: var(--accent);
}
.stat-card.success .stat-value {
    color: var(--success);
}
.stat-card.warning .stat-value {
    color: #e17055;
}

.stat-card .stat-icon {
    position: absolute;
    bottom: -8px;
    right: -8px;
    font-size: 3rem;
    opacity: 0.08;
}

/* Habit list */
.habit-list-title {
    font-size: 1rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.6px;
    color: var(--text-secondary);
    margin-bottom: 14px;
    display: flex;
    align-items: center;
    gap: 8px;
}
.habit-list-title::after {
    content: '';
    flex: 1;
    height: 1px;
    background: var(--border);
    border-radius: 2px;
}

.habit-list {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.habit-item {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    padding: 16px 18px;
    display: flex;
    align-items: center;
    gap: 14px;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
    transition: all var(--transition);
    position: relative;
    cursor: pointer;
    user-select: none;
}
.habit-item:hover {
    box-shadow: var(--shadow-md);
    border-color: #ccc;
}
.dark .habit-item:hover {
    border-color: #444;
}
.habit-item.completed {
    opacity: 0.7;
    background: #f0faf5;
    border-color: #c8e6d0;
}
.dark .habit-item.completed {
    background: #1a2e24;
    border-color: #2a4a34;
}

/* Custom checkbox */
.habit-checkbox {
    width: 26px;
    height: 26px;
    min-width: 26px;
    border-radius: 50%;
    border: 2.5px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.25s ease;
    font-size: 14px;
    color: transparent;
    background: transparent;
}
.habit-item.completed .habit-checkbox {
    background: var(--success);
    border-color: var(--success);
    color: #fff;
    box-shadow: 0 3px 8px rgba(0, 184, 148, 0.3);
}

.habit-info {
    flex: 1;
    min-width: 0;
}
.habit-name {
    font-weight: 700;
    font-size: 1rem;
    letter-spacing: -0.2px;
}
.habit-details {
    display: flex;
    gap: 10px;
    align-items: center;
    margin-top: 4px;
    flex-wrap: wrap;
}
.habit-streak {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    font-size: 0.75rem;
    font-weight: 700;
    background: var(--streak-bg);
    padding: 3px 10px;
    border-radius: 20px;
    color: #e17055;
}
.habit-streak .streak-flame {
    font-size: 0.85rem;
}
.habit-category {
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    padding: 3px 8px;
    border-radius: 4px;
    background: rgba(108, 92, 231, 0.08);
    color: var(--accent);
}
.habit-progress-bar-wrap {
    flex: 1;
    min-width: 60px;
    max-width: 100px;
    height: 5px;
    background: var(--border);
    border-radius: 10px;
    overflow: hidden;
    margin-top: 3px;
}
.habit-progress-bar-fill {
    height: 100%;
    border-radius: 10px;
    transition: width 0.5s ease;
    background: var(--success);
}

.habit-delete {
    opacity: 0;
    transition: opacity var(--transition);
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1.1rem;
    color: var(--danger);
    padding: 4px 8px;
    border-radius: 6px;
}
.habit-item:hover .habit-delete {
    opacity: 1;
}
.habit-delete:hover {
    background: rgba(225, 112, 85, 0.1);
}

/* Add habit form */
.add-habit-section {
    margin-top: 20px;
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    padding: 20px;
    box-shadow: var(--shadow-md);
    border: 2px dashed var(--border);
    display: none;
    animation: slideDown 0.3s ease;
}
.add-habit-section.visible {
    display: block;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-12px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.form-row {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    align-items: flex-end;
}
.form-group {
    display: flex;
    flex-direction: column;
    gap: 5px;
    flex: 1;
    min-width: 120px;
}
.form-group label {
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-secondary);
}
.form-group input,
.form-group select {
    padding: 10px 14px;
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    font-family: inherit;
    background: var(--bg);
    color: var(--text);
    transition: border-color var(--transition);
    width: 100%;
}
.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(108, 92, 231, 0.1);
}

/* Empty state */
.empty-state {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-secondary);
}
.empty-state .empty-icon {
    font-size: 3rem;
    margin-bottom: 12px;
    opacity: 0.6;
}
.empty-state p {
    font-weight: 500;
    margin-bottom: 4px;
}
.empty-state .sub {
    font-size: 0.8rem;
    opacity: 0.7;
}

/* Footer / reset */
.footer-actions {
    display: flex;
    justify-content: center;
    margin-top: 24px;
    gap: 10px;
    flex-wrap: wrap;
}

/* Toast */
.toast {
    position: fixed;
    bottom: 24px;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    background: #2d3436;
    color: #fff;
    padding: 12px 24px;
    border-radius: 30px;
    font-weight: 600;
    font-size: 0.85rem;
    z-index: 999;
    opacity: 0;
    transition: all 0.35s ease;
    pointer-events: none;
    box-shadow: var(--shadow-lg);
}
.dark .toast {
    background: #e0e0e0;
    color: #1a1a2e;
}
.toast.show {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
}

/* Responsive */
@media (max-width: 480px) {
    .header {
        flex-direction: column;
        align-items: flex-start;
    }
    .header-actions {
        width: 100%;
        justify-content: flex-end;
    }
    .stats-row {
        grid-template-columns: repeat(3, 1fr);
        gap: 8px;
    }
    .stat-card {
        padding: 14px 10px;
    }
    .stat-card .stat-value {
        font-size: 1.5rem;
    }
    .stat-card .stat-label {
        font-size: 0.68rem;
    }
    .form-row {
        flex-direction: column;
    }
    .habit-item {
        padding: 12px 14px;
        gap: 10px;
    }
    .habit-delete {
        opacity: 1;
    }
}