/* ========================================
   CSS Variables & Themes
   ======================================== */
:root {
    /* Blue Theme (Default) */
    --primary-50: #eff6ff;
    --primary-100: #dbeafe;
    --primary-200: #bfdbfe;
    --primary-300: #93c5fd;
    --primary-400: #60a5fa;
    --primary-500: #3b82f6;
    --primary-600: #2563eb;
    --primary-700: #1d4ed8;
    --primary-800: #1e40af;
    --primary-900: #1e3a8a;
    
    /* Neutral colors */
    --gray-50: #f9fafb;
    --gray-100: #f3f4f6;
    --gray-200: #e5e7eb;
    --gray-300: #d1d5db;
    --gray-400: #9ca3af;
    --gray-500: #6b7280;
    --gray-600: #4b5563;
    --gray-700: #374151;
    --gray-800: #1f2937;
    --gray-900: #111827;
    
    /* Semantic colors */
    --success: #10b981;
    --warning: #f59e0b;
    --danger: #ef4444;
    
    /* Theme variables */
    --bg-primary: var(--gray-50);
    --bg-secondary: #ffffff;
    --bg-tertiary: var(--gray-100);
    --text-primary: var(--gray-900);
    --text-secondary: var(--gray-600);
    --text-muted: var(--gray-400);
    --border-color: var(--gray-200);
    --shadow-color: rgba(0, 0, 0, 0.1);
    --accent: var(--primary-500);
    --accent-hover: var(--primary-600);
    --accent-light: var(--primary-100);
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    
    /* Border radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    
    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
}

/* ========================================
   Theme Variations
   ======================================== */

/* Blue Dark */
[data-theme="blue-dark"] {
    --bg-primary: var(--gray-900);
    --bg-secondary: var(--gray-800);
    --bg-tertiary: var(--gray-700);
    --text-primary: var(--gray-50);
    --text-secondary: var(--gray-300);
    --text-muted: var(--gray-500);
    --border-color: var(--gray-700);
    --shadow-color: rgba(0, 0, 0, 0.3);
    --accent: var(--primary-400);
    --accent-hover: var(--primary-300);
    --accent-light: var(--primary-900);
}

/* Green Light */
[data-theme="green-light"] {
    --primary-500: #10b981;
    --primary-600: #059669;
    --accent: #10b981;
    --accent-hover: #059669;
    --accent-light: #d1fae5;
}

/* Green Dark */
[data-theme="green-dark"] {
    --bg-primary: var(--gray-900);
    --bg-secondary: var(--gray-800);
    --bg-tertiary: var(--gray-700);
    --text-primary: var(--gray-50);
    --text-secondary: var(--gray-300);
    --text-muted: var(--gray-500);
    --border-color: var(--gray-700);
    --shadow-color: rgba(0, 0, 0, 0.3);
    --accent: #34d399;
    --accent-hover: #6ee7b7;
    --accent-light: #064e3b;
}

/* Purple Light */
[data-theme="purple-light"] {
    --primary-500: #8b5cf6;
    --primary-600: #7c3aed;
    --accent: #8b5cf6;
    --accent-hover: #7c3aed;
    --accent-light: #ede9fe;
}

/* Purple Dark */
[data-theme="purple-dark"] {
    --bg-primary: var(--gray-900);
    --bg-secondary: var(--gray-800);
    --bg-tertiary: var(--gray-700);
    --text-primary: var(--gray-50);
    --text-secondary: var(--gray-300);
    --text-muted: var(--gray-500);
    --border-color: var(--gray-700);
    --shadow-color: rgba(0, 0, 0, 0.3);
    --accent: #a78bfa;
    --accent-hover: #c4b5fd;
    --accent-light: #4c1d95;
}

/* Slate Light */
[data-theme="slate-light"] {
    --accent: #64748b;
    --accent-hover: #475569;
    --accent-light: #f1f5f9;
}

/* Slate Dark */
[data-theme="slate-dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: var(--gray-50);
    --text-secondary: var(--gray-300);
    --text-muted: var(--gray-500);
    --border-color: #334155;
    --shadow-color: rgba(0, 0, 0, 0.3);
    --accent: #94a3b8;
    --accent-hover: #cbd5e1;
    --accent-light: #1e293b;
}

/* ========================================
   Base Styles
   ======================================== */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.5;
    min-height: 100vh;
    transition: background-color var(--transition-normal), color var(--transition-normal);
}

/* ========================================
   Layout
   ======================================== */
.app-container {
    max-width: 900px;
    margin: 0 auto;
    padding: var(--spacing-lg);
}

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

.app-title {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-primary);
}

.header-actions {
    display: flex;
    gap: var(--spacing-sm);
}

/* ========================================
   Buttons
   ======================================== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 0.875rem;
    font-weight: 500;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

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

.btn-primary:hover:not(:disabled) {
    background-color: var(--accent-hover);
}

.btn-secondary {
    background-color: var(--bg-tertiary);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover:not(:disabled) {
    background-color: var(--border-color);
}

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

.btn-ghost:hover:not(:disabled) {
    background-color: var(--bg-tertiary);
    color: var(--text-primary);
}

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

.btn-danger:hover:not(:disabled) {
    background-color: #dc2626;
}

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

.btn-success:hover:not(:disabled) {
    background-color: #059669;
}

.btn-icon {
    width: 36px;
    height: 36px;
    padding: 0;
}

.btn-sm {
    padding: var(--spacing-xs) var(--spacing-sm);
    font-size: 0.75rem;
}

/* ========================================
   Form Elements
   ======================================== */
.form-group {
    margin-bottom: var(--spacing-md);
}

.form-label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
}

.form-input,
.form-textarea,
.form-select {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 0.875rem;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.form-input:focus,
.form-textarea:focus,
.form-select:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-light);
}

.form-textarea {
    resize: vertical;
    min-height: 80px;
}

/* ========================================
   Search & Filter Bar
   ======================================== */
.toolbar {
    display: flex;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
    flex-wrap: wrap;
}

.search-box {
    flex: 1;
    min-width: 200px;
    position: relative;
}

.search-box .search-icon {
    position: absolute;
    left: var(--spacing-sm);
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    pointer-events: none;
}

.search-box .form-input {
    padding-left: 2.25rem;
}

.filter-dropdown {
    position: relative;
    min-width: 180px;
}

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

.filter-menu {
    position: absolute;
    top: calc(100% + 4px);
    left: 0;
    right: 0;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    box-shadow: 0 4px 12px var(--shadow-color);
    z-index: 100;
    max-height: 300px;
    overflow-y: auto;
    display: none;
}

.filter-menu.active {
    display: block;
}

.filter-menu-header {
    display: flex;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm);
    border-bottom: 1px solid var(--border-color);
}

.filter-search {
    padding: var(--spacing-sm);
    border-bottom: 1px solid var(--border-color);
}

.filter-search .form-input {
    padding: var(--spacing-xs) var(--spacing-sm);
    font-size: 0.8125rem;
}

.filter-option {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    cursor: pointer;
    transition: background-color var(--transition-fast);
}

.filter-option:hover {
    background-color: var(--bg-tertiary);
}

.filter-option input[type="checkbox"] {
    accent-color: var(--accent);
}

.filter-empty {
    padding: var(--spacing-md);
    text-align: center;
    color: var(--text-muted);
    font-size: 0.8125rem;
}

/* ========================================
   Tabs
   ======================================== */
.tabs {
    display: flex;
    gap: var(--spacing-xs);
    margin-bottom: var(--spacing-lg);
    border-bottom: 1px solid var(--border-color);
}

.tab {
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    background: none;
    border: none;
    border-bottom: 2px solid transparent;
    cursor: pointer;
    transition: all var(--transition-fast);
    margin-bottom: -1px;
}

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

.tab.active {
    color: var(--accent);
    border-bottom-color: var(--accent);
}

.tab-count {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 20px;
    height: 20px;
    padding: 0 6px;
    font-size: 0.75rem;
    background-color: var(--bg-tertiary);
    border-radius: 10px;
    margin-left: var(--spacing-xs);
}

.tab.active .tab-count {
    background-color: var(--accent-light);
    color: var(--accent);
}

/* ========================================
   Todo List
   ======================================== */
.todo-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.todo-empty {
    text-align: center;
    padding: var(--spacing-xl);
    color: var(--text-muted);
}

/* ========================================
   Todo Card
   ======================================== */
.todo-card {
    display: flex;
    align-items: flex-start;
    gap: var(--spacing-md);
    padding: var(--spacing-md);
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    transition: all var(--transition-fast), transform 0.2s cubic-bezier(0.2, 0, 0, 1);
    cursor: grab;
    position: relative;
}

.todo-card:hover {
    box-shadow: 0 2px 8px var(--shadow-color);
}

/* Dragging states */
.todo-card.dragging {
    opacity: 0.4;
    cursor: grabbing;
    transform: scale(0.98);
    box-shadow: none;
}

.todo-card.drag-over {
    border-color: var(--accent);
    background-color: var(--accent-light);
}


/* Ghost element (clone being dragged) */
.todo-card.drag-ghost {
    position: fixed;
    pointer-events: none;
    z-index: 9999;
    opacity: 0.9;
    transform: rotate(2deg) scale(1.02);
    box-shadow: 0 12px 28px rgba(0, 0, 0, 0.25), 0 8px 10px rgba(0, 0, 0, 0.15);
    cursor: grabbing;
}

.todo-card.completed {
    opacity: 0.7;
}

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

.drag-handle {
    display: flex;
    align-items: center;
    color: var(--text-muted);
    cursor: grab;
    padding: var(--spacing-xs);
    margin: -var(--spacing-xs);
    touch-action: none;
}

.drag-handle:hover {
    color: var(--text-secondary);
}

.todo-checkbox {
    flex-shrink: 0;
    width: 20px;
    height: 20px;
    margin-top: 2px;
    accent-color: var(--accent);
    cursor: pointer;
}

.todo-content {
    flex: 1;
    min-width: 0;
}

.todo-header {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xs);
}

.todo-title {
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--text-primary);
    word-break: break-word;
}

.todo-description {
    font-size: 0.8125rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    word-break: break-word;
}

.todo-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.todo-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
}

.tag {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 2px 8px;
    font-size: 0.75rem;
    background-color: var(--accent-light);
    color: var(--accent);
    border-radius: var(--radius-sm);
}

.tag-remove {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 14px;
    height: 14px;
    background: none;
    border: none;
    color: inherit;
    cursor: pointer;
    opacity: 0.7;
    padding: 0;
}

.tag-remove:hover {
    opacity: 1;
}

.todo-meta {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 0.75rem;
    color: var(--text-muted);
}

.todo-days {
    display: flex;
    align-items: center;
    gap: 4px;
}

.todo-days.warning {
    color: var(--warning);
}

.todo-days.danger {
    color: var(--danger);
}

.todo-actions {
    display: flex;
    gap: var(--spacing-xs);
    opacity: 0;
    transition: opacity var(--transition-fast);
}

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

/* ========================================
   Modal
   ======================================== */
.modal-overlay {
    position: fixed;
    inset: 0;
    background-color: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: flex-start;
    justify-content: center;
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-normal);
    padding: var(--spacing-xl);
    overflow-y: auto;
}

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

.modal {
    width: 100%;
    max-width: 500px;
    background-color: var(--bg-secondary);
    border-radius: var(--radius-lg);
    box-shadow: 0 20px 40px var(--shadow-color);
    overflow: visible;
    transform: scale(0.95) translateY(-20px);
    transition: transform var(--transition-normal);
    margin: auto;
}

.modal-overlay.active .modal {
    transform: scale(1) translateY(0);
}

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

.modal-title {
    font-size: 1.125rem;
    font-weight: 600;
}

.modal-body {
    padding: var(--spacing-lg);
}

.modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: var(--spacing-sm);
    padding: var(--spacing-md) var(--spacing-lg);
    border-top: 1px solid var(--border-color);
}

/* ========================================
   Tag Input
   ======================================== */
.tag-input-container {
    position: relative;
}

.tag-input-wrapper {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm);
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    min-height: 42px;
    cursor: text;
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.tag-input-wrapper:focus-within {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px var(--accent-light);
}

.tag-input-wrapper .tag {
    padding: 4px 8px;
}

.tag-input {
    flex: 1;
    min-width: 120px;
    border: none;
    background: none;
    outline: none;
    font-size: 0.875rem;
    color: var(--text-primary);
}

.tag-input::placeholder {
    color: var(--text-muted);
}

.tag-suggestions {
    position: absolute;
    top: calc(100% + 4px);
    left: 0;
    right: 0;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    box-shadow: 0 4px 12px var(--shadow-color);
    z-index: 1100;
    max-height: 180px;
    overflow-y: auto;
    display: none;
}

.tag-suggestions.active {
    display: block;
}

.tag-suggestion {
    padding: var(--spacing-sm) var(--spacing-md);
    cursor: pointer;
    transition: background-color var(--transition-fast);
    font-size: 0.875rem;
}

.tag-suggestion:hover,
.tag-suggestion.selected {
    background-color: var(--bg-tertiary);
}

.tag-suggestion-new {
    color: var(--accent);
    font-style: italic;
}

/* ========================================
   Theme Selector
   ======================================== */
.theme-menu {
    position: absolute;
    top: calc(100% + 4px);
    right: 0;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    box-shadow: 0 4px 12px var(--shadow-color);
    z-index: 100;
    min-width: 180px;
    display: none;
}

.theme-menu.active {
    display: block;
}

.theme-option {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    cursor: pointer;
    transition: background-color var(--transition-fast);
    font-size: 0.875rem;
    width: 100%;
    background: none;
    border: none;
    color: var(--text-primary);
    text-align: left;
}

.theme-option:hover {
    background-color: var(--bg-tertiary);
}

.theme-option.active {
    color: var(--accent);
}

.theme-color {
    width: 16px;
    height: 16px;
    border-radius: 50%;
    border: 2px solid var(--border-color);
    flex-shrink: 0;
}

.theme-selector {
    position: relative;
}

.theme-label {
    flex: 1;
}

.theme-mode {
    font-size: 0.7rem;
    color: var(--text-muted);
    margin-left: auto;
    padding: 2px 6px;
    background-color: var(--bg-tertiary);
    border-radius: var(--radius-sm);
}

/* ========================================
   SVG Icons
   ======================================== */
.icon {
    width: 18px;
    height: 18px;
    flex-shrink: 0;
}

.icon-sm {
    width: 14px;
    height: 14px;
}

.icon-lg {
    width: 24px;
    height: 24px;
}

/* ========================================
   Utilities
   ======================================== */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* ========================================
   Responsive
   ======================================== */
@media (max-width: 640px) {
    .app-container {
        padding: var(--spacing-md);
    }
    
    .app-header {
        flex-direction: column;
        align-items: flex-start;
        gap: var(--spacing-md);
    }
    
    .header-actions {
        width: 100%;
        justify-content: flex-end;
    }
    
    .toolbar {
        flex-direction: column;
    }
    
    .search-box,
    .filter-dropdown {
        width: 100%;
    }
    
    .todo-actions {
        opacity: 1;
    }
    
    .modal-overlay {
        padding: var(--spacing-md);
    }
    
    .modal {
        margin: var(--spacing-md) auto;
    }

    /* ========================================
    Loading Indicator
    ======================================== */
    .loading {
        display: flex;
        flex-direction: column;
        align-items: center;
        justify-content: center;
        gap: var(--spacing-md);
        padding: var(--spacing-xl);
        color: var(--text-muted);
    }

    .loading-spinner {
        width: 32px;
        height: 32px;
        border: 3px solid var(--border-color);
        border-top-color: var(--accent);
        border-radius: 50%;
        animation: spin 0.8s linear infinite;
    }

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

    /* ========================================
    User Greeting
    ======================================== */
    .user-greeting {
        font-size: 0.875rem;
        color: var(--text-secondary);
        margin-right: var(--spacing-sm);
    }

    /* ========================================
    Login Screen
    ======================================== */
    .login-overlay {
        top: 0;
        left: 0;
        right: 0;
        bottom: 0;
        width: 100%;
        height: 100%;
        background-color: var(--bg-primary);
        display: flex;
        align-items: center;
        justify-content: center;
        z-index: 2000;
        margin: 0;
        padding: 0;
    }

    .login-card {
        width: 100%;
        max-width: 360px;
        padding: var(--spacing-xl);
        background-color: var(--bg-secondary);
        border: 1px solid var(--border-color);
        border-radius: var(--radius-lg);
        box-shadow: 0 4px 20px var(--shadow-color);
        margin-top: 50px;
        margin-left: 50px;
    }

    .login-title {
        font-size: 1.5rem;
        font-weight: 600;
        text-align: center;
        margin-bottom: var(--spacing-xs);
        color: var(--text-primary);
    }

    .login-subtitle {
        font-size: 0.875rem;
        color: var(--text-muted);
        text-align: center;
        margin-bottom: var(--spacing-lg);
    }

    .login-btn {
        width: 100%;
        padding: var(--spacing-sm) var(--spacing-md);
        margin-top: var(--spacing-sm);
    }

    .login-error {
        display: none;
        padding: var(--spacing-sm);
        margin-bottom: var(--spacing-sm);
        background-color: #fef2f2;
        border: 1px solid #fecaca;
        border-radius: var(--radius-md);
        color: #dc2626;
        font-size: 0.875rem;
        text-align: center;
    }

    [data-theme*="dark"] .login-error {
        background-color: #450a0a;
        border-color: #7f1d1d;
        color: #fca5a5;
    }
}

/* ========================================
   Save Status Indicator
   ======================================== */
.app-title-row {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.save-status {
    font-size: 0.75rem;
    padding: 4px 10px;
    border-radius: var(--radius-sm);
    transition: all var(--transition-normal);
    opacity: 1;
}

.save-status:empty {
    display: none;
}

.save-status.saving {
    background-color: var(--accent-light);
    color: var(--accent);
}

.save-status.saved {
    background-color: #d1fae5;
    color: #059669;
}

.save-status.error {
    background-color: #fef2f2;
    color: #dc2626;
}

.save-status.fade-out {
    opacity: 0;
}

[data-theme*="dark"] .save-status.saved {
    background-color: #064e3b;
    color: #6ee7b7;
}

[data-theme*="dark"] .save-status.error {
    background-color: #450a0a;
    color: #fca5a5;
}

/* ========================================
   Mobile Touch Support
   ======================================== */
@media (max-width: 640px) {
    .drag-handle {
        padding: var(--spacing-sm);
        margin: calc(-1 * var(--spacing-sm));
        touch-action: none;
    }
}

/* Prevent text selection while dragging */
.todo-card.dragging,
.drag-ghost {
    user-select: none;
    -webkit-user-select: none;
}