:root {
    --bg-primary: #f5f7fa;
    --bg-secondary: #ffffff;
    --text-primary: #2c3e50;
    --text-secondary: #7f8c8d;
    --border-color: #e1e8ed;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-hover: 0 4px 12px rgba(0, 0, 0, 0.15);

    /* Quadrant colors */
    --urgent-important: #ff6b6b;
    --urgent-not-important: #feca57;
    --not-urgent-important: #48dbfb;
    --not-urgent-not-important: #a29bfe;

    /* Kanban colors */
    --backlog: #95a5a6;
    --todo: #3498db;
    --in-progress: #f39c12;
    --done: #2ecc71;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
}

.container {
    max-width: 1600px;
    margin: 0 auto;
    padding: 20px;
}

/* Header */
header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    padding: 20px;
    background: var(--bg-secondary);
    border-radius: 12px;
    box-shadow: var(--shadow);
}

header h1 {
    font-size: 28px;
    font-weight: 600;
}

.controls {
    display: flex;
    gap: 12px;
    align-items: center;
    /* allow buttons to wrap on narrow screens instead of overflowing */
    flex-wrap: wrap;
}

/* Buttons */
.view-btn {
    padding: 10px 20px;
    border: 2px solid var(--border-color);
    background: var(--bg-secondary);
    color: var(--text-primary);
    border-radius: 8px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 500;
    transition: all 0.3s;
}

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

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

.primary-btn {
    padding: 10px 20px;
    background: #3498db;
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 500;
    transition: all 0.3s;
}

.primary-btn:hover {
    background: #2980b9;
    transform: translateY(-2px);
    box-shadow: var(--shadow);
}

.icon-btn {
    padding: 10px 15px;
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: 8px;
    cursor: pointer;
    font-size: 18px;
    transition: all 0.3s;
}

.icon-btn:hover {
    /* large rotation is jarring and can cause layout issues; use a subtle rotate+scale */
    transform: rotate(20deg) scale(1.03);
}

/* View Containers */
.view-container {
    display: none;
}

.view-container.active {
    display: block;
    animation: fadeIn 0.3s;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Eisenhower Matrix */
.eisenhower-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    margin-top: 20px;
}

.quadrant {
    background: var(--bg-secondary);
    border-radius: 12px;
    padding: 20px;
    box-shadow: var(--shadow);
    /* reduce default min-height so smaller screens don't get excessive overflow */
    min-height: 320px;
    border-left: 4px solid;
}

.quadrant.urgent-important {
    border-color: var(--urgent-important);
}

.quadrant.urgent-not-important {
    border-color: var(--urgent-not-important);
}

.quadrant.not-urgent-important {
    border-color: var(--not-urgent-important);
}

.quadrant.not-urgent-not-important {
    border-color: var(--not-urgent-not-important);
}

.quadrant-header {
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 2px solid var(--border-color);
}

.quadrant-header h2 {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 5px;
}

.quadrant-header .subtitle {
    font-size: 13px;
    color: var(--text-secondary);
}

/* Kanban Board */
.kanban-board {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
    margin-top: 20px;
}

.kanban-column {
    background: var(--bg-secondary);
    border-radius: 12px;
    padding: 20px;
    box-shadow: var(--shadow);
    /* more reasonable column height for narrow screens */
    min-height: 420px;
}

.column-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding-bottom: 15px;
    border-bottom: 2px solid var(--border-color);
}

.column-header h2 {
    font-size: 18px;
    font-weight: 600;
}

.column-header .count {
    background: var(--border-color);
    color: var(--text-primary);
    padding: 4px 12px;
    border-radius: 12px;
    font-size: 14px;
    font-weight: 600;
}

/* Todo Items */
.todo-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
    /* prevent lists from growing indefinitely and allow internal scrolling */
    max-height: calc(60vh - 220px);
    overflow-y: auto;
    padding-right: 6px; /* room for scrollbar without shifting layout */
}

.todo-item {
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 15px;
    cursor: grab;
    transition: all 0.3s;
}

.todo-item:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-2px);
}

.todo-item.dragging {
    opacity: 0.5;
    cursor: grabbing;
}

.todo-item.overdue {
    border-left: 4px solid #e74c3c;
}

.todo-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 8px;
}

.todo-text {
    flex: 1;
    font-size: 15px;
    font-weight: 500;
    line-height: 1.4;
}

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

.todo-actions {
    display: flex;
    gap: 8px;
}

.todo-action-btn {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 16px;
    padding: 4px;
    opacity: 0.6;
    transition: opacity 0.2s;
}

.todo-action-btn:hover {
    opacity: 1;
}

.todo-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 10px;
    font-size: 13px;
}

.todo-badge {
    padding: 4px 10px;
    border-radius: 12px;
    font-size: 12px;
    font-weight: 500;
    white-space: nowrap;
}

.todo-badge.project {
    background: #e8f4f8;
    color: #2980b9;
}

.todo-badge.due-date {
    background: #fff3cd;
    color: #856404;
}

.todo-badge.due-date.overdue {
    background: #f8d7da;
    color: #721c24;
}

.todo-badge.tag {
    background: #e9ecef;
    color: #495057;
}

.todo-indicators {
    display: flex;
    gap: 4px;
    font-size: 14px;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    z-index: 1000;
    align-items: center;
    justify-content: center;
}

.modal.active {
    display: flex;
}

.modal-content {
    background: var(--bg-secondary);
    border-radius: 12px;
    padding: 30px;
    max-width: 500px;
    width: 90%;
    max-height: 90vh;
    overflow-y: auto;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 25px;
}

.modal-header h2 {
    font-size: 24px;
    font-weight: 600;
}

.close-btn {
    background: none;
    border: none;
    font-size: 28px;
    cursor: pointer;
    color: var(--text-secondary);
    transition: color 0.2s;
}

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

/* Form */
.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    font-size: 14px;
    color: var(--text-primary);
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 12px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 14px;
    font-family: inherit;
    transition: border-color 0.3s;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: #3498db;
}

.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 15px;
}

.form-actions {
    display: flex;
    gap: 12px;
    justify-content: flex-end;
    margin-top: 25px;
}

.cancel-btn {
    padding: 10px 20px;
    background: var(--bg-primary);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
    border-radius: 8px;
    cursor: pointer;
    font-size: 14px;
    font-weight: 500;
    transition: all 0.3s;
}

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

/* Empty State */
.empty-state {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-secondary);
}

.empty-state p {
    font-size: 14px;
    margin-top: 10px;
}

/* Drag and Drop */
.todo-list.drag-over {
    background: rgba(52, 152, 219, 0.1);
    border: 2px dashed #3498db;
    border-radius: 8px;
}

/* Projects Grid View */
.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 20px;
    padding: 10px;
}

.project-card {
    background: var(--bg-secondary);
    border: 2px solid var(--border-color);
    border-radius: 12px;
    overflow: hidden;
    transition: all 0.3s ease;
    box-shadow: var(--shadow);
}

.project-card:hover {
    box-shadow: var(--shadow-hover);
    transform: translateY(-2px);
}

.project-header {
    padding: 20px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    cursor: pointer;
    user-select: none;
    transition: all 0.2s;
}

.project-header:hover {
    background: linear-gradient(135deg, #5a67d8 0%, #6b3fa0 100%);
}

.project-header:active {
    transform: scale(0.98);
}

.project-title {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 12px;
}

.project-icon {
    font-size: 28px;
    line-height: 1;
}

.project-name {
    font-size: 20px;
    font-weight: 600;
    text-transform: capitalize;
}

.project-stats {
    display: flex;
    align-items: center;
    gap: 15px;
    font-size: 13px;
    opacity: 0.95;
}

.pending-count {
    font-weight: 600;
}

.total-count {
    opacity: 0.8;
}

.expand-icon {
    margin-left: auto;
    font-size: 16px;
    transition: transform 0.3s ease;
}

.project-card.expanded .expand-icon {
    transform: rotate(180deg);
}

.project-todos {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease-out, padding 0.4s ease-out;
    padding: 0 20px;
}

.project-card.expanded .project-todos {
    max-height: 2000px;
    padding: 20px;
    transition: max-height 0.5s ease-in, padding 0.5s ease-in;
}

.project-card.collapsed .project-todos {
    max-height: 0;
    padding: 0 20px;
}

.project-todos .todo-list {
    max-height: none;
}

/* Completed tasks toggle */
.completed-toggle-container {
    padding: 15px 0;
    text-align: center;
    border-top: 1px solid var(--border-color);
    margin-top: 15px;
}

.show-completed-btn {
    padding: 8px 16px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 13px;
    transition: all 0.2s;
}

.show-completed-btn:hover {
    background: var(--bg-secondary);
    border-color: var(--text-primary);
    color: var(--text-primary);
}

.completed-todos-container {
    margin-top: 15px;
    padding-top: 15px;
    border-top: 2px dashed var(--border-color);
}

.completed-todos-container .todo-item {
    opacity: 0.7;
}

.completed-count-footer {
    text-align: center;
    padding: 10px;
    color: var(--text-secondary);
    font-size: 13px;
    font-style: italic;
}

.loading, .error, .no-completed {
    text-align: center;
    padding: 20px;
    color: var(--text-secondary);
    font-style: italic;
}

.error {
    color: #e74c3c;
}

/* Undo toast */
.undo-toast {
    position: fixed;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%);
    background: #2c3e50;
    color: white;
    padding: 15px 25px;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
    display: flex;
    align-items: center;
    gap: 20px;
    z-index: 10000;
    animation: slideUp 0.3s ease-out;
}

@keyframes slideUp {
    from {
        transform: translateX(-50%) translateY(100px);
        opacity: 0;
    }
    to {
        transform: translateX(-50%) translateY(0);
        opacity: 1;
    }
}

.undo-toast .undo-btn {
    padding: 6px 14px;
    background: #3498db;
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-size: 13px;
    font-weight: 500;
    transition: background 0.2s;
}

.undo-toast .undo-btn:hover {
    background: #2980b9;
}

/* Drag over effect for project todos */
.project-todos.drag-over {
    background: rgba(52, 152, 219, 0.1);
    border: 2px dashed #3498db;
    border-radius: 8px;
}

/* Responsive */
@media (max-width: 1200px) {
    .kanban-board {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .eisenhower-grid {
        grid-template-columns: 1fr;
    }

    .kanban-board {
        grid-template-columns: 1fr;
    }

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

    header {
        flex-direction: column;
        gap: 15px;
    }

    .controls {
        width: 100%;
        justify-content: space-between;
    }
}