/* ==========================================================================
   TaskMaster - Main Stylesheet
   A modern task management application with beautiful UI
   ========================================================================== */

/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* CSS Custom Properties for theming and consistency */
:root {
    /* Color Palette - Light Theme */
    --primary-color: #6366f1;
    --primary-hover: #5855eb;
    --secondary-color: #f8fafc;
    --accent-color: #06b6d4;
    --success-color: #10b981;
    --warning-color: #f59e0b;
    --danger-color: #ef4444;
    
    /* Neutral Colors */
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --border-color: #e2e8f0;
    --background-primary: #ffffff;
    --background-secondary: #f8fafc;
    --background-tertiary: #f1f5f9;
    
    /* Shadow System */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1), 0 8px 10px -6px rgb(0 0 0 / 0.1);
    
    /* Spacing Scale */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Border Radius Scale */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    
    /* Animation Timing */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.2s ease;
    --transition-slow: 0.3s ease;
}

/* Dark Theme Overrides */
[data-theme="dark"] {
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-muted: #64748b;
    --border-color: #334155;
    --background-primary: #0f172a;
    --background-secondary: #1e293b;
    --background-tertiary: #334155;
}

/* Base Typography and Layout */
body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--background-secondary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color var(--transition-normal), color var(--transition-normal);
}

/* Main App Container */
.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ==========================================================================
   Header Styles
   ========================================================================== */

.header {
    background: var(--background-primary);
    border-bottom: 1px solid var(--border-color);
    padding: var(--spacing-md) 0;
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: blur(10px);
}

.header-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 var(--spacing-lg);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--primary-color);
}

.logo i {
    font-size: 1.5rem;
}

.logo h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

.theme-toggle {
    background: var(--background-tertiary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-sm);
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.theme-toggle:hover {
    background: var(--background-secondary);
    color: var(--text-primary);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

/* ==========================================================================
   Main Content Layout
   ========================================================================== */

.main-content {
    flex: 1;
    display: flex;
    max-width: 1400px;
    margin: 0 auto;
    width: 100%;
    padding: var(--spacing-lg);
    gap: var(--spacing-xl);
}

/* ==========================================================================
   Sidebar Styles
   ========================================================================== */

.sidebar {
    width: 280px;
    background: var(--background-primary);
    border-radius: var(--radius-xl);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-lg);
    height: fit-content;
    position: sticky;
    top: 100px;
}

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

.sidebar-header h3 {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
}

.add-category-btn {
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.add-category-btn:hover {
    background: var(--primary-hover);
    transform: scale(1.05);
}

.category-list {
    list-style: none;
    margin-bottom: var(--spacing-xl);
}

.category-item {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    margin-bottom: var(--spacing-xs);
    position: relative;
}

.category-item:hover {
    background: var(--background-tertiary);
}

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

.category-item i {
    width: 16px;
    text-align: center;
}

.category-item span:first-of-type {
    flex: 1;
    font-weight: 500;
}

.task-count {
    background: var(--background-tertiary);
    color: var(--text-secondary);
    padding: 2px 8px;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 600;
    min-width: 20px;
    text-align: center;
}

.category-item.active .task-count {
    background: rgba(255, 255, 255, 0.2);
    color: white;
}

.sidebar-footer {
    border-top: 1px solid var(--border-color);
    padding-top: var(--spacing-lg);
}

.stats {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.stat-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.stat-label {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

.stat-value {
    font-weight: 600;
    color: var(--text-primary);
}

/* ==========================================================================
   Task Area Styles
   ========================================================================== */

.task-area {
    flex: 1;
    background: var(--background-primary);
    border-radius: var(--radius-xl);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-lg);
}

.task-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: var(--spacing-xl);
    gap: var(--spacing-lg);
}

.task-header-left h2 {
    font-size: 1.875rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: var(--spacing-xs);
}

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

.task-header-right {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.sort-select {
    background: var(--background-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: var(--spacing-sm) var(--spacing-md);
    color: var(--text-primary);
    font-size: 0.875rem;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.sort-select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

.add-task-btn {
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--radius-md);
    padding: var(--spacing-sm) var(--spacing-lg);
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

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

/* ==========================================================================
   Task List Styles
   ========================================================================== */

.task-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.task-item {
    background: var(--background-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    transition: all var(--transition-normal);
    cursor: pointer;
    position: relative;
    overflow: hidden;
}

.task-item:hover {
    border-color: var(--primary-color);
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.task-item.completed {
    opacity: 0.7;
    background: var(--background-tertiary);
}

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

.task-item.overdue {
    border-color: var(--danger-color);
    background: rgba(239, 68, 68, 0.05);
}

.task-item.overdue .task-due-date {
    color: var(--danger-color);
}

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

.task-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--spacing-xs);
    transition: color var(--transition-fast);
}

.task-description {
    color: var(--text-secondary);
    font-size: 0.875rem;
    line-height: 1.5;
    margin-bottom: var(--spacing-md);
}

.task-meta {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    flex-wrap: wrap;
}

.task-category {
    background: var(--background-tertiary);
    color: var(--text-secondary);
    padding: 4px 12px;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 500;
    text-transform: capitalize;
}

.task-priority {
    padding: 4px 12px;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
    font-weight: 500;
    text-transform: capitalize;
}

.task-priority.high {
    background: rgba(239, 68, 68, 0.1);
    color: var(--danger-color);
}

.task-priority.medium {
    background: rgba(245, 158, 11, 0.1);
    color: var(--warning-color);
}

.task-priority.low {
    background: rgba(16, 185, 129, 0.1);
    color: var(--success-color);
}

.task-due-date {
    color: var(--text-secondary);
    font-size: 0.875rem;
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

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

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

.task-action-btn {
    background: var(--background-primary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 6px;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.task-action-btn:hover {
    background: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

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