/* ============================================
   CSS VARIABLES - DESIGN SYSTEM
   ============================================ */

:root {
    /* Colors - Light Mode */
    --color-primary-500: #3B82F6;
    --color-primary-600: #2563EB;
    --color-primary-700: #1D4ED8;
    
    --color-gray-50: #F9FAFB;
    --color-gray-100: #F3F4F6;
    --color-gray-200: #E5E7EB;
    --color-gray-300: #D1D5DB;
    --color-gray-400: #9CA3AF;
    --color-gray-600: #4B5563;
    --color-gray-700: #374151;
    --color-gray-800: #1F2937;
    --color-gray-900: #111827;
    
    --color-success: #10B981;
    --color-error: #EF4444;
    
    /* Semantic Colors */
    --bg-primary: #FFFFFF;
    --bg-secondary: var(--color-gray-50);
    --bg-card: var(--color-gray-100);
    --text-primary: var(--color-gray-900);
    --text-secondary: var(--color-gray-600);
    --border-color: var(--color-gray-200);
    
    /* Typography */
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-mono: 'JetBrains Mono', 'Courier New', monospace;
    
    /* Spacing */
    --space-1: 0.25rem;
    --space-2: 0.5rem;
    --space-3: 0.75rem;
    --space-4: 1rem;
    --space-5: 1.25rem;
    --space-6: 1.5rem;
    --space-8: 2rem;
    --space-10: 2.5rem;
    --space-12: 3rem;
    
    /* Border Radius */
    --radius-sm: 0.25rem;
    --radius-base: 0.5rem;
    --radius-md: 0.75rem;
    --radius-lg: 1rem;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-base: 0 1px 3px rgba(0, 0, 0, 0.1), 0 1px 2px rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.1), 0 2px 4px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1), 0 4px 6px rgba(0, 0, 0, 0.05);
    
    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-base: 0.2s ease;
    --transition-slow: 0.3s ease;
}

/* Dark Mode */
[data-theme="dark"] {
    --color-primary-500: #60A5FA;
    --color-primary-600: #3B82F6;
    --color-primary-700: #2563EB;
    
    --bg-primary: var(--color-gray-900);
    --bg-secondary: var(--color-gray-800);
    --bg-card: var(--color-gray-800);
    --text-primary: var(--color-gray-50);
    --text-secondary: var(--color-gray-400);
    --border-color: var(--color-gray-700);
    
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-base: 0 1px 3px rgba(0, 0, 0, 0.4), 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4), 0 2px 4px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.5), 0 4px 6px rgba(0, 0, 0, 0.4);
}

/* ============================================
   RESET & BASE STYLES
   ============================================ */

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    background: var(--bg-secondary);
    color: var(--text-primary);
    line-height: 1.5;
    transition: background-color var(--transition-base), color var(--transition-base);
}

/* ============================================
   LAYOUT
   ============================================ */

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--space-4);
}

/* Header */
.header {
    background: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    padding: var(--space-4) 0;
    position: sticky;
    top: 0;
    z-index: 100;
    transition: background-color var(--transition-base), border-color var(--transition-base);
}

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

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

.theme-toggle {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-base);
    padding: var(--space-2) var(--space-4);
    cursor: pointer;
    font-size: 1.25rem;
    transition: all var(--transition-base);
}

.theme-toggle:hover {
    background: var(--border-color);
    transform: translateY(-1px);
}

/* Main */
.main {
    padding: var(--space-8) 0;
}

.tool-header {
    text-align: center;
    margin-bottom: var(--space-8);
}

.tool-header h2 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: var(--space-2);
    color: var(--text-primary);
}

.tool-header p {
    font-size: 1.125rem;
    color: var(--text-secondary);
}

/* Tool Grid */
.tool-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-8);
    margin-bottom: var(--space-12);
}

@media (max-width: 1024px) {
    .tool-grid {
        grid-template-columns: 1fr;
        gap: var(--space-6);
    }
}

/* ============================================
   PICKER SECTION
   ============================================ */

.picker-section {
    background: var(--bg-primary);
    padding: var(--space-6);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-base);
}

/* Color Square */
.color-square-wrapper {
    position: relative;
    width: 100%;
    max-width: 300px;
    margin: 0 auto var(--space-6);
}

.color-square {
    width: 100%;
    height: 300px;
    border-radius: var(--radius-md);
    cursor: crosshair;
    box-shadow: var(--shadow-md);
    border: 1px solid rgba(0, 0, 0, 0.1);
}

.color-cursor {
    position: absolute;
    width: 20px;
    height: 20px;
    border: 3px solid white;
    border-radius: 50%;
    pointer-events: none;
    transform: translate(-50%, -50%);
    box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.3), 0 2px 4px rgba(0, 0, 0, 0.2);
    transition: all var(--transition-fast);
}

/* Sliders */
.slider-wrapper {
    margin-bottom: var(--space-4);
}

.slider-label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: var(--space-2);
}

.hue-slider-track,
.opacity-slider-track {
    position: relative;
    height: 40px;
    border-radius: var(--radius-base);
    overflow: hidden;
}

.hue-slider,
.opacity-slider {
    width: 100%;
    height: 100%;
    -webkit-appearance: none;
    appearance: none;
    background: transparent;
    cursor: pointer;
    position: relative;
    z-index: 2;
}

/* Hue Slider Background */
.hue-slider-track {
    background: linear-gradient(to right, 
        hsl(0, 100%, 50%),
        hsl(60, 100%, 50%),
        hsl(120, 100%, 50%),
        hsl(180, 100%, 50%),
        hsl(240, 100%, 50%),
        hsl(300, 100%, 50%),
        hsl(360, 100%, 50%)
    );
}

/* Opacity Slider Background */
.opacity-slider-track {
    background: 
        linear-gradient(to right, transparent, currentColor),
        repeating-conic-gradient(#ccc 0% 25%, white 0% 50%) 50% / 20px 20px;
}

.opacity-value {
    position: absolute;
    right: var(--space-2);
    top: 50%;
    transform: translateY(-50%);
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-primary);
    background: var(--bg-primary);
    padding: var(--space-1) var(--space-2);
    border-radius: var(--radius-sm);
    pointer-events: none;
}

/* Slider Thumb */
.hue-slider::-webkit-slider-thumb,
.opacity-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 20px;
    height: 40px;
    background: white;
    border: 2px solid var(--color-gray-300);
    border-radius: var(--radius-sm);
    cursor: pointer;
    box-shadow: var(--shadow-md);
}

.hue-slider::-moz-range-thumb,
.opacity-slider::-moz-range-thumb {
    width: 20px;
    height: 40px;
    background: white;
    border: 2px solid var(--color-gray-300);
    border-radius: var(--radius-sm);
    cursor: pointer;
    box-shadow: var(--shadow-md);
}

/* ============================================
   OUTPUT SECTION
   ============================================ */

.output-section {
    background: var(--bg-primary);
    padding: var(--space-6);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-base);
}

/* Color Preview */
.color-preview-card {
    margin-bottom: var(--space-6);
}

.color-preview-card h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: var(--space-3);
    color: var(--text-primary);
}

.color-preview {
    width: 100%;
    height: 120px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    border: 1px solid rgba(0, 0, 0, 0.1);
    background: #3B82F6;
}

/* Color Formats */
.color-formats h3 {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: var(--space-4);
    color: var(--text-primary);
}

.format-group {
    margin-bottom: var(--space-3);
}

.format-group label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: var(--space-2);
}

.input-with-copy {
    display: flex;
    gap: var(--space-2);
}

.color-input {
    flex: 1;
    padding: var(--space-2) var(--space-3);
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-base);
    font-family: var(--font-mono);
    font-size: 0.875rem;
    color: var(--text-primary);
    transition: all var(--transition-base);
}

.color-input:focus {
    outline: none;
    border-color: var(--color-primary-500);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.copy-btn {
    padding: var(--space-2) var(--space-3);
    background: var(--color-primary-500);
    color: white;
    border: none;
    border-radius: var(--radius-base);
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: var(--space-1);
    transition: all var(--transition-base);
    white-space: nowrap;
}

.copy-btn:hover {
    background: var(--color-primary-600);
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

.copy-btn:active {
    transform: translateY(0);
}

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

.copy-icon {
    font-size: 1rem;
}

/* ============================================
   SECTIONS
   ============================================ */

.shades-section,
.harmony-section,
.recent-section {
    background: var(--bg-primary);
    padding: var(--space-6);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-base);
    margin-bottom: var(--space-6);
}

.shades-section h3,
.harmony-section h3,
.recent-section h3 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: var(--space-2);
    color: var(--text-primary);
}

.section-description {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: var(--space-4);
}

/* Shades Grid */
.shades-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(48px, 1fr));
    gap: var(--space-2);
}

.shade-swatch {
    aspect-ratio: 1;
    border-radius: var(--radius-base);
    cursor: pointer;
    transition: all var(--transition-base);
    border: 1px solid rgba(0, 0, 0, 0.1);
    position: relative;
}

.shade-swatch:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-md);
    z-index: 10;
}

.shade-swatch:active {
    transform: scale(0.95);
}

/* Harmony Section */
.harmony-tabs {
    display: flex;
    gap: var(--space-2);
    margin-bottom: var(--space-4);
    flex-wrap: wrap;
}

.harmony-tab {
    padding: var(--space-2) var(--space-4);
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-base);
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-base);
}

.harmony-tab:hover {
    background: var(--border-color);
}

.harmony-tab.active {
    background: var(--color-primary-500);
    color: white;
    border-color: var(--color-primary-500);
}

.harmony-colors {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(80px, 1fr));
    gap: var(--space-4);
}

.harmony-color {
    text-align: center;
}

.harmony-swatch {
    width: 100%;
    aspect-ratio: 1;
    border-radius: var(--radius-base);
    cursor: pointer;
    transition: all var(--transition-base);
    border: 1px solid rgba(0, 0, 0, 0.1);
    margin-bottom: var(--space-2);
}

.harmony-swatch:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-md);
}

.harmony-label {
    font-size: 0.75rem;
    font-family: var(--font-mono);
    color: var(--text-secondary);
}

/* Recent Colors */
.recent-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-4);
}

.clear-btn {
    padding: var(--space-2) var(--space-3);
    background: transparent;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-base);
    font-size: 0.875rem;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-base);
}

.clear-btn:hover {
    background: var(--color-error);
    color: white;
    border-color: var(--color-error);
}

.recent-colors {
    display: flex;
    gap: var(--space-2);
    flex-wrap: wrap;
}

.recent-swatch {
    width: 48px;
    height: 48px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: all var(--transition-base);
    border: 1px solid rgba(0, 0, 0, 0.1);
}

.recent-swatch:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-md);
}

.recent-empty {
    color: var(--text-secondary);
    font-size: 0.875rem;
    font-style: italic;
}

/* ============================================
   FOOTER
   ============================================ */

.footer {
    background: var(--bg-primary);
    border-top: 1px solid var(--border-color);
    padding: var(--space-6) 0;
    text-align: center;
    margin-top: var(--space-12);
}

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

/* ============================================
   TOAST NOTIFICATION
   ============================================ */

.toast {
    position: fixed;
    bottom: var(--space-6);
    right: var(--space-6);
    background: var(--color-success);
    color: white;
    padding: var(--space-3) var(--space-5);
    border-radius: var(--radius-base);
    box-shadow: var(--shadow-lg);
    display: flex;
    align-items: center;
    gap: var(--space-2);
    font-weight: 500;
    opacity: 0;
    transform: translateY(20px);
    transition: all var(--transition-base);
    pointer-events: none;
    z-index: 1000;
}

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

.toast-icon {
    font-size: 1.25rem;
}

/* ============================================
   RESPONSIVE
   ============================================ */

@media (max-width: 768px) {
    .container {
        padding: 0 var(--space-3);
    }

    .tool-header h2 {
        font-size: 1.5rem;
    }

    .tool-header p {
        font-size: 1rem;
    }

    .color-square {
        height: 280px;
    }

    .color-preview {
        height: 80px;
    }

    .harmony-tabs {
        font-size: 0.75rem;
    }

    .harmony-tab {
        padding: var(--space-2) var(--space-3);
    }

    .shades-grid {
        grid-template-columns: repeat(5, 1fr);
    }
}

@media (max-width: 480px) {
    .logo h1 {
        font-size: 1.25rem;
    }

    .copy-text {
        display: none;
    }

    .harmony-colors {
        grid-template-columns: repeat(3, 1fr);
    }
}

/* ============================================
   ANIMATIONS
   ============================================ */

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

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

/* ============================================
   ACCESSIBILITY
   ============================================ */

/* Focus visible for keyboard navigation */
*:focus-visible {
    outline: 2px solid var(--color-primary-500);
    outline-offset: 2px;
}

/* Reduced motion */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}