:root {
    /* Light Theme Colors */
    --bg-primary: #f8f9fa;
    --bg-secondary: #ffffff;
    --text-primary: #212529;
    --text-secondary: #6c757d;
    --accent-primary: #007bff;
    --accent-secondary: #6610f2;
    --border-color: #dee2e6;
    --card-shadow: 0 4px 6px rgba(0,0,0,0.1);
    
    /* Status Colors */
    --status-not-started: #6c757d;
    --status-started: #007bff;
    --status-completed: #28a745;
    --status-on-hold: #ffc107; 
    --status-resumed: #17a2b8;
    
    /* Priority Colors */
    --priority-not-important: #6c757d;
    --priority-important: #fd7e14;
    --priority-urgent: #dc3545;
    --priority-not-urgent: #20c997;
    
    /* Spacing */
    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 1.5rem;
    --space-xl: 2rem;
    
    /* Border radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 1rem;
    
    /* Transition */
    --transition-speed: 0.3s;
}

/* Dark Theme Colors */
[data-theme="dark"] {
    --bg-primary: #121212;
    --bg-secondary: #1e1e1e;
    --text-primary: #f8f9fa;
    --text-secondary: #adb5bd;
    --border-color: #343a40;
    --card-shadow: 0 4px 6px rgba(0,0,0,0.3);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    transition: background-color var(--transition-speed), color var(--transition-speed);
    min-height: 100vh;
}

/* Header & Navigation */
header {
    background-color: var(--bg-secondary);
    box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 var(--space-md);
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--space-md) 0;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--accent-primary);
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

.nav-actions {
    display: flex;
    gap: var(--space-md);
    align-items: center;
}

.user-info {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-md);
    background-color: rgba(0,0,0,0.05);
    border-radius: var(--radius-md);
}

[data-theme="dark"] .user-info {
    background-color: rgba(255,255,255,0.05);
}

#user-name {
    font-weight: 500;
}

.btn {
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--radius-md);
    border: none;
    cursor: pointer;
    font-weight: 500;
    transition: all var(--transition-speed);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
}

.btn-primary {
    background-color: var(--accent-primary);
    color: white;
}

.btn-primary:hover {
    opacity: 0.9;
}

.btn-icon {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    padding: 0;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background-color: transparent;
    color: var(--text-primary);
}

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

[data-theme="dark"] .btn-icon:hover {
    background-color: rgba(255,255,255,0.05);
}

.btn-sm {
    padding: var(--space-xs) var(--space-sm);
    font-size: 0.875rem;
}

/* Main Content */
main {
    padding: var(--space-lg) 0;
}

.toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-lg);
    flex-wrap: wrap;
    gap: var(--space-md);
}

.view-options {
    display: flex;
    gap: var(--space-sm);
}

.view-option {
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--radius-md);
    cursor: pointer;
    border: 1px solid var(--border-color);
    background-color: var(--bg-secondary);
    color: var(--text-primary);
}

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

.filters {
    display: flex;
    gap: var(--space-sm);
    flex-wrap: wrap;
}

select {
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    cursor: pointer;
}

/* Connection Status */
.connection-status {
    margin-bottom: var(--space-md);
}

.offline-indicator {
    padding: var(--space-sm) var(--space-md);
    background-color: rgba(255, 193, 7, 0.2);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    color: #856404;
}

.hidden {
    display: none;
}

/* Kanban Board */
.kanban-view {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: var(--space-lg);
    margin-top: var(--space-lg);
}

.kanban-column {
    background-color: var(--bg-secondary);
    border-radius: var(--radius-md);
    padding: var(--space-md);
    border: 1px solid var(--border-color);
    min-height: 300px;
}

/* Status Column View */
.status-columns-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--space-md);
    margin-top: var(--space-md);
}

.status-column {
    background-color: rgba(255,255,255,0.05);
    border-radius: var(--radius-sm);
    padding: var(--space-sm);
    min-height: 200px;
}

.column-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-md);
    padding-bottom: var(--space-sm);
    border-bottom: 1px solid var(--border-color);
}

.column-title {
    font-weight: 600;
    font-size: 1.1rem;
}

.task-count {
    background-color: var(--accent-primary);
    color: white;
    border-radius: var(--radius-sm);
    padding: 2px 8px;
    font-size: 0.8rem;
}

.task-card {
    background-color: var(--bg-primary);
    border-radius: var(--radius-md);
    padding: var(--space-md);
    margin-bottom: var(--space-md);
    box-shadow: var(--card-shadow);
    cursor: pointer;
    transition: transform var(--transition-speed), box-shadow var(--transition-speed);
    border-left: 4px solid var(--status-not-started);
    position: relative;
}

.task-card:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 12px rgba(0,0,0,0.1);
}

.task-card.status-not-started { border-left-color: var(--status-not-started); }
.task-card.status-started { border-left-color: var(--status-started); }
.task-card.status-completed { 
    border-left-color: var(--status-completed); 
    opacity: 0.8;
}
.task-card.status-on-hold { border-left-color: var(--status-on-hold); }
.task-card.status-resumed { border-left-color: var(--status-resumed); }

.task-quick-actions {
    position: absolute;
    top: var(--space-xs);
    right: var(--space-xs);
    display: flex;
    gap: 2px;
    opacity: 0;
    transition: opacity var(--transition-speed);
}

.task-card:hover .task-quick-actions {
    opacity: 1;
}

.task-quick-action {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--bg-secondary);
    border: none;
    cursor: pointer;
    font-size: 0.7rem;
    transition: background-color var(--transition-speed);
}

.task-quick-action:hover {
    background-color: var(--border-color);
}

.task-title {
    font-weight: 600;
    margin-bottom: var(--space-sm);
}

.task-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: var(--space-md);
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.task-tags {
    display: flex;
    gap: var(--space-xs);
    flex-wrap: wrap;
    margin-top: var(--space-sm);
}

.task-tag {
    background-color: var(--accent-secondary);
    color: white;
    padding: 2px 8px;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
}

.task-priority {
    display: inline-block;
    margin-left: auto;
    padding: 2px 8px;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
}

.priority-not-important { background-color: var(--priority-not-important); color: white; }
.priority-important { background-color: var(--priority-important); color: white; }
.priority-urgent { background-color: var(--priority-urgent); color: white; }
.priority-not-urgent { background-color: var(--priority-not-urgent); color: white; }

/* List View */
.list-view {
    background-color: var(--bg-secondary);
    border-radius: var(--radius-md);
    overflow: hidden;
    border: 1px solid var(--border-color);
    display: block;
}

.list-header {
    display: grid;
    grid-template-columns: 3fr 1fr 1fr 1fr 0.5fr;
    padding: var(--space-md);
    font-weight: 600;
    border-bottom: 1px solid var(--border-color);
}

.list-task {
    display: grid;
    grid-template-columns: 3fr 1fr 1fr 1fr 0.5fr;
    padding: var(--space-md);
    border-bottom: 1px solid var(--border-color);
    align-items: center;
    transition: background-color var(--transition-speed);
    cursor: pointer;
}

.list-task:hover {
    background-color: rgba(0,0,0,0.02);
}

[data-theme="dark"] .list-task:hover {
    background-color: rgba(255,255,255,0.02);
}

.task-actions {
    display: flex;
    gap: var(--space-sm);
    justify-content: flex-end;
}

/* Calendar View */
.calendar-view {
    display: block;
    background-color: var(--bg-secondary);
    border-radius: var(--radius-md);
    overflow: hidden;
    border: 1px solid var(--border-color);
}

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

.calendar-month {
    font-weight: 600;
    font-size: 1.2rem;
}

.calendar-nav {
    display: flex;
    gap: var(--space-sm);
}

.calendar-grid {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    grid-template-rows: auto;
    gap: 1px;
    background-color: var(--border-color);
}

.calendar-day-names {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    background-color: var(--bg-secondary);
    text-align: center;
    font-weight: 600;
    padding: var(--space-sm) 0;
}

.calendar-day {
    background-color: var(--bg-secondary);
    min-height: 100px;
    padding: var(--space-sm);
    position: relative;
}

.calendar-date {
    font-size: 0.85rem;
    margin-bottom: var(--space-sm);
    color: var(--text-secondary);
}

.calendar-day.today .calendar-date {
    background-color: var(--accent-primary);
    color: white;
    border-radius: 50%;
    width: 24px;
    height: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.calendar-day.other-month {
    opacity: 0.5;
}

.calendar-task {
    font-size: 0.8rem;
    padding: 2px 4px;
    margin-bottom: 2px;
    border-radius: var(--radius-sm);
    background-color: var(--accent-primary);
    color: white;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    cursor: pointer;
}

/* Task Modal */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0,0,0,0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: opacity var(--transition-speed), visibility var(--transition-speed);
}

.modal-overlay.active {
    opacity: 1;
    visibility: visible;
}

.modal {
    background-color: var(--bg-secondary);
    border-radius: var(--radius-lg);
    width: 90%;
    max-width: 600px;
    max-height: 90vh;
    overflow-y: auto;
    padding: var(--space-lg);
    position: relative;
    transform: translateY(20px);
    transition: transform var(--transition-speed);
}

.modal-overlay.active .modal {
    transform: translateY(0);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-lg);
}

.modal-title {
    font-size: 1.3rem;
    font-weight: 600;
}

.modal-close {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1.5rem;
    color: var(--text-secondary);
}

.form-group {
    margin-bottom: var(--space-md);
}

label {
    display: block;
    margin-bottom: var(--space-xs);
    font-weight: 500;
}

input[type="text"],
textarea,
select {
    width: 100%;
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-family: inherit;
    font-size: 1rem;
}

input[type="date"] {
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    font-family: inherit;
}

textarea {
    resize: vertical;
    min-height: 100px;
}

.tag-input-container {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-xs);
    margin-top: var(--space-xs);
    padding: var(--space-sm);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    min-height: 42px;
}

.tag-item {
    display: flex;
    align-items: center;
    background-color: var(--accent-secondary);
    color: white;
    padding: 2px 8px;
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
    gap: var(--space-xs);
}

.tag-remove {
    cursor: pointer;
    font-size: 0.7rem;
}

.tag-input {
    flex: 1;
    min-width: 60px;
    border: none;
    background: transparent;
    color: var(--text-primary);
    outline: none;
    font-size: 0.9rem;
}

.modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: var(--space-md);
    margin-top: var(--space-lg);
}

.btn-secondary {
    background-color: var(--text-secondary);
    color: white;
}

.btn-secondary:hover {
    opacity: 0.9;
}

.btn-danger {
    background-color: var(--priority-urgent);
    color: white;
}

.btn-danger:hover {
    opacity: 0.9;
}

/* Toast Notifications */
.toast-container {
    position: fixed;
    bottom: var(--space-lg);
    right: var(--space-lg);
    z-index: 1000;
}

.toast {
    background-color: var(--bg-secondary);
    border-radius: var(--radius-md);
    padding: var(--space-md);
    margin-top: var(--space-sm);
    box-shadow: var(--card-shadow);
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    transform: translateX(100%);
    opacity: 0;
    transition: transform var(--transition-speed), opacity var(--transition-speed);
}

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

.toast-success {
    border-left: 4px solid var(--status-completed);
}

.toast-error {
    border-left: 4px solid var(--priority-urgent);
}

.toast-info {
    border-left: 4px solid var(--accent-primary);
}

.toast-icon {
    font-size: 1.2rem;
}

.toast-success .toast-icon {
    color: var(--status-completed);
}

.toast-error .toast-icon {
    color: var(--priority-urgent);
}

.toast-info .toast-icon {
    color: var(--accent-primary);
}

/* Import/Export Modal */
.import-file {
    margin-top: var(--space-sm);
}

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

.empty-state-icon {
    font-size: 3rem;
    margin-bottom: var(--space-md);
}

/* Drag and Drop */
.dragging {
    opacity: 0.5;
}

.drag-over {
    background-color: rgba(0, 123, 255, 0.1);
}

/* Responsive Adjustments */
@media (max-width: 768px) {
    .toolbar {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .kanban-view {
        grid-template-columns: 1fr;
        overflow-x: auto;
    }
    
    .list-header, .list-task {
        grid-template-columns: 2fr 1fr 1fr 0.5fr;
    }
    
    .list-header > div:nth-child(3),
    .list-task > div:nth-child(3) {
        display: none;
    }
    
    .calendar-day-names > div,
    .calendar-grid > div {
        font-size: 0.8rem;
    }
    
    .calendar-day {
        min-height: 80px;
    }
}

@media (max-width: 480px) {
    .navbar {
        flex-direction: column;
        gap: var(--space-sm);
        align-items: flex-start;
    }
    
    .nav-actions {
        width: 100%;
        justify-content: space-between;
    }
    
    .list-header, .list-task {
        grid-template-columns: 2fr 1fr 0.5fr;
    }
    
    .list-header > div:nth-child(2),
    .list-task > div:nth-child(2) {
        display: none;
    }
}