:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --success-color: #22c55e;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    --light-bg: #f8fafc;
    --dark-bg: #0f172a;
    --card-bg: #ffffff;
    --card-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-light: #f1f5f9;
    --border-color: #e2e8f0;
    --transition-normal: all 0.3s ease;
    --transition-fast: all 0.15s ease;
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 1rem;
    --font-primary: 'Montserrat', sans-serif;
    --font-secondary: 'Open Sans', sans-serif;
}

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

body {
    font-family: var(--font-secondary);
    background-color: var(--light-bg);
    color: var(--text-primary);
    font-size: 1rem;
    line-height: 1.5;
    min-height: 100vh;
    transition: var(--transition-normal);
}

body.dark-mode {
    --light-bg: #0f172a;
    --dark-bg: #1e293b;
    --card-bg: #1e293b;
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --border-color: #334155;
}

button {
    cursor: pointer;
    font-family: var(--font-primary);
}

input[type="text"],
input[type="search"] {
    font-family: var(--font-secondary);
}

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

 .app-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    background-color: var(--card-bg);
    box-shadow: var(--card-shadow);
    position: sticky;
    top: 0;
    z-index: 10;
}

.logo-container {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.logo-icon {
    font-size: 1.75rem;
    color: var(--primary-color);
}

.app-header h1 {
    font-family: var(--font-primary);
    font-weight: 700;
    font-size: 1.5rem;
    background: linear-gradient(135deg, var(--primary-color), #8b5cf6);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
}

.theme-toggle {
    background: none;
    border: none;
    font-size: 1.25rem;
    color: var(--text-secondary);
    padding: 0.5rem;
    border-radius: var(--radius-md);
    transition: var(--transition-fast);
}

.theme-toggle:hover {
    color: var(--primary-color);
    background-color: var(--border-color);
}

 .dashboard {
    display: flex;
    flex: 1;
    height: calc(100vh - 4rem);
}

 .sidebar {
    width: 250px;
    background-color: var(--card-bg);
    border-right: 1px solid var(--border-color);
    padding: 1.5rem 1rem;
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.user-profile {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.avatar {
    width: 60px;
    height: 60px;
    background-color: var(--primary-color);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
}

.user-profile p {
    font-weight: 600;
    color: var(--text-secondary);
}

.nav-menu {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.nav-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem 1rem;
    border-radius: var(--radius-md);
    background: none;
    border: none;
    color: var(--text-secondary);
    font-weight: 500;
    transition: var(--transition-fast);
    text-align: left;
}

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

.nav-item.active {
    background-color: var(--primary-color);
    color: white;
}

.task-stats {
    margin-top: auto;
}

.stat-card {
    background: linear-gradient(135deg, #6366f1, #8b5cf6);
    border-radius: var(--radius-md);
    padding: 1.25rem;
    color: white;
    text-align: center;
}

.stat-card h3 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 0.25rem;
}

.stat-card p {
    font-size: 0.875rem;
    opacity: 0.9;
}

 .task-board {
    flex: 1;
    padding: 1.5rem;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.board-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.board-header h2 {
    font-family: var(--font-primary);
    font-weight: 600;
    font-size: 1.5rem;
}

.task-actions {
    display: flex;
    gap: 1rem;
    align-items: center;
}

.search-container {
    position: relative;
}

.search-container i {
    position: absolute;
    left: 0.75rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary);
}

#search-tasks {
    padding: 0.625rem 1rem 0.625rem 2.5rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    width: 250px;
    background-color: var(--card-bg);
    color: var(--text-primary);
    transition: var(--transition-fast);
}

#search-tasks:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.25);
}

.add-task-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.625rem 1.25rem;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    font-weight: 500;
    transition: var(--transition-fast);
}

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

.task-input-panel {
    background-color: var(--card-bg);
    border-radius: var(--radius-md);
    box-shadow: var(--card-shadow);
    padding: 1.5rem;
    border: 1px solid var(--border-color);
    transition: var(--transition-normal);
    transform-origin: top center;
}

.task-input-panel.hidden {
    display: none;
    opacity: 0;
    transform: scaleY(0.8);
}

#new-task {
    width: 100%;
    padding: 0.875rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 1rem;
    background-color: var(--card-bg);
    color: var(--text-primary);
    margin-bottom: 1rem;
}

#new-task:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.25);
}

.task-input-actions {
    display: flex;
    justify-content: flex-end;
    gap: 0.75rem;
}

#cancel-add {
    padding: 0.625rem 1.25rem;
    background: none;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-weight: 500;
}

#add-button {
    padding: 0.625rem 1.25rem;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    font-weight: 500;
}

 .task-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.25rem;
}

.task-card {
    background-color: var(--card-bg);
    border-radius: var(--radius-md);
    box-shadow: var(--card-shadow);
    padding: 1.25rem;
    border: 1px solid var(--border-color);
    transition: var(--transition-normal);
    position: relative;
    animation: fade-in 0.3s ease-out;
}

.task-card:hover {
    transform: translateY(-6px) scale(1.01);
    box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
}

.task-card.completed {
    border-left: 4px solid var(--success-color);
}

.task-card.completed .task-text {
    text-decoration: line-through;
    color: var(--text-secondary);
}

.task-header {
    display: flex;
    align-items: center;
    margin-bottom: 0.75rem;
}

.task-checkbox {
    appearance: none;
    -webkit-appearance: none;
    width: 20px;
    height: 20px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    margin-right: 0.75rem;
    position: relative;
    cursor: pointer;
    transition: var(--transition-fast);
}

.task-checkbox:checked {
    background-color: var(--success-color);
    border-color: var(--success-color);
}

.task-checkbox:checked::after {
    content: '✓';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: white;
    font-size: 0.75rem;
}

.task-text {
    font-weight: 500;
    font-size: 1.125rem;
    line-height: 1.4;
    word-break: break-word;
    margin-bottom: 0.5rem;
    transition: var(--transition-normal);
}

.task-card-actions {
    display: flex;
    gap: 0.5rem;
    margin-top: 1rem;
    justify-content: flex-end;
}

.task-card-actions button {
    background: none;
    border: none;
    font-size: 1rem;
    padding: 0.375rem;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    transition: var(--transition-fast);
}

.task-card-actions button:hover {
    background-color: rgba(0, 0, 0, 0.05);
}

.task-card-actions .edit-btn:hover {
    color: var(--primary-color);
}

.task-card-actions .delete-btn:hover {
    color: var(--danger-color);
}

/* Animations */
@keyframes fade-in {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

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

/* Responsive Design */
@media (max-width: 768px) {
    .dashboard {
        flex-direction: column;
        height: auto;
    }

    .sidebar {
        width: 100%;
        border-right: none;
        border-bottom: 1px solid var(--border-color);
        padding: 1rem;
    }

    .user-profile {
        flex-direction: row;
        gap: 1rem;
        padding-bottom: 1rem;
    }

    .nav-menu {
        flex-direction: row;
        overflow-x: auto;
        padding-bottom: 0.5rem;
    }

    .nav-item {
        flex-shrink: 0;
    }

    .task-stats {
        margin-top: 1rem;
    }

    .board-header {
        flex-direction: column;
        align-items: flex-start;
    }

    .task-actions {
        width: 100%;
        flex-direction: column;
    }

    .search-container,
    #search-tasks {
        width: 100%;
    }

    .add-task-btn {
        width: 100%;
        justify-content: center;
    }

    .task-grid {
        grid-template-columns: 1fr;
    }
}

.task-extra-fields {
    display: flex;
    margin-bottom: 1rem;
    gap: 1rem;
}

.task-extra-fields select {
    flex: 1;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background-color: var(--card-bg);
    color: var(--text-primary);
}

.task-meta {
    display: flex;
    gap: 0.5rem;
    margin: 0.5rem 0;
}

.badge {
    padding: 0.25rem 0.6rem;
    border-radius: 999px;
    font-size: 0.7rem;
    font-weight: 600;
}

/* Category Colors */
.category-Work {
    background-color: rgba(99, 102, 241, 0.15);
    color: #6366f1;
}

.category-Academic {
    background-color: rgba(139, 92, 246, 0.15);
    color: #8b5cf6;
}

.category-Personal {
    background-color: rgba(34, 197, 94, 0.15);
    color: #22c55e;
}

/* Priority Colors */
.priority-High {
    background-color: rgba(239, 68, 68, 0.15);
    color: #ef4444;
}

.priority-Medium {
    background-color: rgba(245, 158, 11, 0.15);
    color: #f59e0b;
}

.priority-Low {
    background-color: rgba(148, 163, 184, 0.2);
    color: #64748b;
}

.task-content {
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
}

.empty-state {
    opacity: 0.7;
    animation: fade-in 0.4s ease-in-out;
}

#new-task:focus {
    transform: scale(1.01);
}