:root {
    --primary-color: #2196f3;
    --primary-dark: #1976d2;
    --primary-light: #bbdefb;
    --secondary-color: #ff4081;
    --background-color: #f5f5f5;
    --card-background: #ffffff;
    --text-color: #333333;
    --text-secondary: #666666;
    --border-color: #e0e0e0;
    --success-color: #4caf50;
    --warning-color: #ff9800;
    --danger-color: #f44336;
    --transition-speed: 0.3s;
    --border-radius: 8px;
    --shadow-small: 0 2px 4px rgba(0,0,0,0.1);
    --shadow-medium: 0 4px 6px rgba(0,0,0,0.1);
    --shadow-large: 0 8px 16px rgba(0,0,0,0.1);
}

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

body {
    font-family: 'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

/* Navigation */
.navbar {
    background-color: var(--card-background);
    padding: 1rem;
    box-shadow: var(--shadow-small);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-content {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand {
    color: var(--primary-color);
    text-decoration: none;
    font-size: 1.5rem;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.nav-brand i {
    font-size: 1.8rem;
}

/* Container */
.container {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 1rem;
}

/* Topics Grid */
.topics-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    flex-wrap: wrap;
    gap: 1rem;
}

.topics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 1.5rem;
    min-height: 200px;
}

.topic-card {
    background-color: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-small);
    transition: transform var(--transition-speed), box-shadow var(--transition-speed);
    position: relative;
}

.topic-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-medium);
}

.topic-content {
    padding: 1.5rem;
    cursor: pointer;
}

.topic-actions {
    position: absolute;
    top: 0.5rem;
    right: 0.5rem;
    display: flex;
    gap: 0.5rem;
    opacity: 0;
    transition: opacity var(--transition-speed);
}

.topic-card:hover .topic-actions {
    opacity: 1;
}

.action-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 0.5rem;
    border-radius: 50%;
    transition: all var(--transition-speed);
    display: flex;
    align-items: center;
    justify-content: center;
}

.action-btn:hover {
    background-color: rgba(0,0,0,0.05);
    color: var(--danger-color);
}

.action-btn.delete-btn:hover {
    color: var(--danger-color);
}

.topic-content h2 {
    margin-bottom: 0.5rem;
    color: var(--primary-color);
    font-size: 1.25rem;
}

.topic-description {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 1rem;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.topic-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 1rem;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

/* Full Page Topic View */
.topic-page {
    background-color: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-medium);
    padding: 2rem;
    min-height: 80vh;
}

.topic-page-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border-color);
}

.topic-page-title {
    color: var(--primary-color);
    font-size: 2rem;
    font-weight: 600;
}

.topic-page-description {
    color: var(--text-secondary);
    margin-bottom: 2rem;
    font-size: 1.1rem;
}

/* Forms and Inputs */
.input-group {
    position: relative;
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.input-with-button {
    display: flex;
    gap: 0.5rem;
    width: 100%;
}

input[type="text"],
textarea {
    width: 100%;
    padding: 0.8rem;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: border-color var(--transition-speed);
    background-color: var(--card-background);
}

input[type="text"]:focus,
textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}

.submit-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 0.8rem;
    border-radius: 50%;
    cursor: pointer;
    transition: background-color var(--transition-speed);
    display: flex;
    align-items: center;
    justify-content: center;
    aspect-ratio: 1;
}

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

.submit-btn i {
    font-size: 1.2rem;
}

/* Animations */
@keyframes fadeOutLeft {
    from {
        opacity: 1;
        transform: translateX(0);
    }
    to {
        opacity: 0;
        transform: translateX(-100%);
    }
}

@keyframes fadeInRight {
    from {
        opacity: 0;
        transform: translateX(100%);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.fade-out-left {
    animation: fadeOutLeft 0.5s ease-out forwards;
}

.fade-in-right {
    animation: fadeInRight 0.5s ease-out forwards;
}

/* Responsive Design */
@media (max-width: 768px) {
    .topics-header {
        flex-direction: column;
        align-items: stretch;
    }

    .topic-page {
        padding: 1rem;
    }

    .topic-page-header {
        flex-direction: column;
        gap: 1rem;
    }

    .topic-actions {
        opacity: 1;
        position: static;
        justify-content: flex-end;
        padding: 0.5rem;
    }
}

/* Loading States */
.loading {
    position: relative;
}

.loading::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(255,255,255,0.8);
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--border-radius);
}

/* Drag and Drop */
.sortable-ghost {
    opacity: 0.5;
    background-color: var(--primary-light);
}

.sortable-chosen {
    background-color: var(--card-background);
    box-shadow: var(--shadow-large);
}

.drag-handle {
    cursor: grab;
    color: var(--text-secondary);
    padding: 0.5rem;
}

.drag-handle:active {
    cursor: grabbing;
}

.hidden {
    display: none;
}

.toast-container {
    position: fixed;
    bottom: 20px;
    right: 20px;
    z-index: 1000;
}

.toast {
    background-color: var(--success-color);
    color: white;
    padding: 1rem 2rem;
    border-radius: var(--border-radius);
    margin-top: 0.5rem;
    transform: translateX(100%);
    opacity: 0;
    transition: all 0.3s ease-in-out;
}

.toast.error {
    background-color: var(--danger-color);
}

.toast.show {
    transform: translateX(0);
    opacity: 1;
}

.add-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: background-color var(--transition-speed);
}

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

.form-buttons {
    display: flex;
    justify-content: flex-end;
    gap: 1rem;
}

.cancel-btn {
    background-color: #757575;
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: background-color var(--transition-speed);
}

.cancel-btn:hover {
    background-color: #616161;
}

/* Task Styling */
.tasks-container {
    margin-top: 2rem;
}

.tasks-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.task-item {
    background-color: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-small);
    transition: transform var(--transition-speed), box-shadow var(--transition-speed);
    border: 1px solid var(--border-color);
}

.task-item:hover {
    transform: translateX(4px);
    box-shadow: var(--shadow-medium);
}

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

.task-checkbox {
    display: flex;
    align-items: center;
}

.task-checkbox input[type="checkbox"] {
    width: 1.2rem;
    height: 1.2rem;
    cursor: pointer;
    border: 2px solid var(--primary-color);
    border-radius: 4px;
    appearance: none;
    -webkit-appearance: none;
    position: relative;
    transition: all var(--transition-speed);
}

.task-checkbox input[type="checkbox"]:checked {
    background-color: var(--primary-color);
}

.task-checkbox input[type="checkbox"]:checked::after {
    content: '✓';
    position: absolute;
    color: white;
    font-size: 0.8rem;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.task-text {
    flex-grow: 1;
    font-size: 1rem;
    color: var(--text-color);
}

.task-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
    opacity: 0.7;
    transition: opacity var(--transition-speed);
}

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

.status-select {
    padding: 0.5rem;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    background-color: var(--card-background);
    color: var(--text-color);
    cursor: pointer;
    font-size: 0.9rem;
    transition: border-color var(--transition-speed);
}

.status-select:hover {
    border-color: var(--primary-color);
}

.status-select option {
    padding: 0.5rem;
}

/* Subtask Styling */
.subtask {
    margin-left: 2rem;
    border-left: 2px solid var(--primary-color);
}

/* Confirmation Dialog Styling */
.confirmation-dialog {
    background-color: var(--card-background);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-large);
    padding: 2rem;
    max-width: 400px;
    width: 90%;
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    z-index: 1100;
    animation: dialogSlideIn 0.3s ease-out;
}

@keyframes dialogSlideIn {
    from {
        transform: translate(-50%, -60%);
        opacity: 0;
    }
    to {
        transform: translate(-50%, -50%);
        opacity: 1;
    }
}

.confirmation-dialog h2 {
    color: var(--danger-color);
    margin-bottom: 1rem;
    font-size: 1.5rem;
    font-weight: 600;
}

.confirmation-dialog p {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    line-height: 1.5;
}

.dialog-buttons {
    display: flex;
    justify-content: flex-end;
    gap: 1rem;
}

.confirm-btn {
    background-color: var(--danger-color);
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-weight: 500;
    transition: all var(--transition-speed);
}

.confirm-btn:hover {
    background-color: #d32f2f;
    transform: translateY(-1px);
}

.cancel-btn {
    background-color: #757575;
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-weight: 500;
    transition: all var(--transition-speed);
}

.cancel-btn:hover {
    background-color: #616161;
    transform: translateY(-1px);
}

.overlay {
    background-color: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(2px);
    transition: all var(--transition-speed);
}

/* Task Filters */
.task-filters {
    display: flex;
    gap: 0.5rem;
    margin: 1.5rem 0;
    flex-wrap: wrap;
}

.filter-btn {
    background-color: var(--card-background);
    border: 1px solid var(--border-color);
    padding: 0.5rem 1rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: all var(--transition-speed);
    color: var(--text-secondary);
}

.filter-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

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

/* Task Status Colors */
.task-item[data-status="Completed"] {
    background-color: #f8fff8;
    border-left: 4px solid var(--success-color);
}

.task-item[data-status="In Progress"] {
    background-color: #fff8f0;
    border-left: 4px solid var(--warning-color);
}

.task-item[data-status="Not Required"] {
    background-color: #f5f5f5;
    border-left: 4px solid var(--text-secondary);
}

/* Mobile Optimizations */
@media (max-width: 768px) {
    .task-content {
        flex-wrap: wrap;
    }

    .task-actions {
        width: 100%;
        justify-content: flex-end;
        margin-top: 1rem;
        opacity: 1;
    }

    .status-select {
        max-width: 140px;
    }

    .task-filters {
        justify-content: center;
    }

    .confirmation-dialog {
        width: 95%;
        margin: 1rem;
    }
}

/* Loading Animation */
.loading::after {
    content: '';
    width: 1.5rem;
    height: 1.5rem;
    border: 2px solid var(--primary-color);
    border-top-color: transparent;
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

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

/* Toast Notifications Enhancement */
.toast {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    box-shadow: var(--shadow-medium);
    font-weight: 500;
}

.toast::before {
    font-family: "Font Awesome 6 Free";
    font-weight: 900;
}

.toast.success::before {
    content: "\f00c";
}

.toast.error::before {
    content: "\f071";
}

.popup-menu {
    position: absolute;
    background: white;
    border: 1px solid #ddd;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    padding: 12px;
    z-index: 1000;
    transform-origin: top left;
    animation: popupGrow 0.2s ease-out;
}

.popup-menu.hidden {
    display: none;
}

@keyframes popupGrow {
    from {
        transform: scale(0.95);
        opacity: 0;
    }
    to {
        transform: scale(1);
        opacity: 1;
    }
}

.bulk-actions {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    background: white;
    border-radius: 25px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    padding: 10px 20px;
    display: flex;
    gap: 10px;
    z-index: 1000;
    animation: popupGrow 0.2s ease-out;
}

.bulk-actions.hidden {
    display: none;
}

.date-selector-btn {
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
    color: #666;
}

.date-selector-btn:hover {
    color: #333;
}

/* Notes styling */
.notes-section {
    width: 100%;
    margin: 8px 0;
    position: relative;
}

.notes-input-wrapper {
    display: flex;
    align-items: center;
    gap: 8px;
    background: #f5f5f5;
    border-radius: 6px;
    padding: 4px 8px;
    transition: all 0.2s ease;
}

.notes-input-wrapper:hover {
    background: #eeeeee;
}

.note-input {
    flex: 1;
    border: none;
    background: transparent;
    padding: 4px;
    font-size: 0.9em;
    color: #666;
}

.note-input:focus {
    outline: none;
    color: #333;
}

.notes-toggle {
    background: none;
    border: none;
    padding: 4px 8px;
    cursor: pointer;
    color: #666;
    transition: transform 0.2s ease;
}

.notes-toggle:hover {
    color: #333;
}

.notes-toggle i {
    transition: transform 0.2s ease;
}

.notes-toggle i.fa-chevron-up {
    transform: rotate(180deg);
}

.notes-dropdown {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: white;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
    padding: 8px;
    margin-top: 4px;
    z-index: 100;
    max-height: 300px;
    overflow-y: auto;
    transform-origin: top center;
    transition: all 0.2s ease;
}

.notes-dropdown.hidden {
    opacity: 0;
    transform: scaleY(0.95);
    pointer-events: none;
}

.note-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 8px;
    border-radius: 4px;
    margin-bottom: 4px;
    background: #f8f8f8;
    transition: all 0.2s ease;
}

.note-item:last-child {
    margin-bottom: 0;
}

.note-item:hover {
    background: #f0f0f0;
}

.note-content {
    flex: 1;
    font-size: 0.9em;
    color: #444;
    margin-right: 8px;
    word-break: break-word;
}

.note-actions {
    display: flex;
    gap: 4px;
    opacity: 0;
    transition: opacity 0.2s ease;
}

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

.note-actions button {
    background: none;
    border: none;
    padding: 4px;
    cursor: pointer;
    color: #666;
    border-radius: 4px;
    transition: all 0.2s ease;
}

.note-actions button:hover {
    color: #333;
    background: rgba(0,0,0,0.05);
}

.note-edit-input {
    flex: 1;
    border: none;
    background: white;
    padding: 4px 8px;
    border-radius: 4px;
    font-size: 0.9em;
    color: #333;
    box-shadow: 0 0 0 1px #ddd;
}

.note-edit-input:focus {
    outline: none;
    box-shadow: 0 0 0 2px #007bff;
}

/* Nested tasks styling */
.task-item {
    position: relative;
    transition: all 0.2s ease;
}

.task-item.subtask {
    margin-left: 24px;
    border-left: 2px solid #e0e0e0;
    padding-left: 12px;
}

.task-item.subtask::before {
    content: '';
    position: absolute;
    left: -2px;
    top: 0;
    bottom: 0;
    width: 2px;
    background: #e0e0e0;
    opacity: 0;
    transition: opacity 0.2s ease;
}

.task-item.subtask:hover::before {
    opacity: 1;
    background: #007bff;
}

.sortable-ghost {
    opacity: 0.5;
    background: #f8f8f8;
}

.sortable-chosen {
    background: white;
    box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

/* Drag handle improvements */
.drag-handle {
    cursor: grab;
    opacity: 0.5;
    transition: all 0.2s ease;
}

.drag-handle:hover {
    opacity: 1;
}

.drag-handle:active {
    cursor: grabbing;
}

/* Scrollbar styling for notes dropdown */
.notes-dropdown::-webkit-scrollbar {
    width: 8px;
}

.notes-dropdown::-webkit-scrollbar-track {
    background: #f1f1f1;
    border-radius: 4px;
}

.notes-dropdown::-webkit-scrollbar-thumb {
    background: #ccc;
    border-radius: 4px;
}

.notes-dropdown::-webkit-scrollbar-thumb:hover {
    background: #999;
}

/* Animation for new notes */
@keyframes noteAdd {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.note-item {
    animation: noteAdd 0.2s ease-out;
}

/* Empty state for notes */
.notes-dropdown:empty::after {
    content: 'No notes yet';
    display: block;
    text-align: center;
    padding: 12px;
    color: #999;
    font-style: italic;
}

/* Task nesting indicator */
.task-item.can-nest {
    border: 2px dashed #007bff;
}

.task-item.is-nesting {
    background: #f0f7ff;
}