/* ===================================
   CSS Custom Properties / Variables
   =================================== */
:root {
    /* Colors */
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary: #8b5cf6;
    --success: #10b981;
    --danger: #ef4444;
    --warning: #f59e0b;
    
    /* Neutrals */
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    
    /* Border radius */
    --radius-sm: 0.5rem;
    --radius-md: 1rem;
    --radius-lg: 1.5rem;
    
    /* Shadows */
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.5);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.6);
    
    /* Transitions */
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 50%, #0f172a 100%);
    background-attachment: fixed;
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
}

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

/* ===================================
   Header
   =================================== */
.header {
    background: rgba(15, 23, 42, 0.8);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    padding: var(--spacing-md) 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

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

.logo {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    font-size: 1.5rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.logo-icon {
    font-size: 2rem;
}

.github-btn {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-xs) var(--spacing-md);
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    border-radius: var(--radius-md);
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
}

.github-btn:hover {
    background: rgba(255, 255, 255, 0.15);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.star-count {
    background: rgba(255, 255, 255, 0.2);
    padding: 0.25rem 0.5rem;
    border-radius: 0.5rem;
    font-size: 0.875rem;
}

/* ===================================
   Main Content
   =================================== */
.main {
    padding: var(--spacing-xl) 0;
    min-height: calc(100vh - 200px);
}

/* Hero Section */
.hero {
    text-align: center;
    margin-bottom: var(--spacing-xl);
}

.hero-title {
    font-size: clamp(2rem, 5vw, 3.5rem);
    font-weight: 800;
    margin-bottom: var(--spacing-sm);
    background: linear-gradient(135deg, var(--primary-light), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: clamp(1rem, 2vw, 1.25rem);
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* ===================================
   Upload Section
   =================================== */
.upload-section {
    margin-bottom: var(--spacing-xl);
}

.upload-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

.upload-box {
    position: relative;
    background: rgba(255, 255, 255, 0.05);
    border: 2px dashed rgba(255, 255, 255, 0.2);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    min-height: 300px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: var(--transition);
    overflow: hidden;
}

.upload-box:hover {
    border-color: var(--primary);
    background: rgba(99, 102, 241, 0.1);
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.upload-box.dragging {
    border-color: var(--primary-light);
    background: rgba(99, 102, 241, 0.2);
    transform: scale(1.02);
}

.upload-box.has-image {
    border-style: solid;
    border-color: var(--success);
    background: rgba(16, 185, 129, 0.1);
}

.upload-content {
    text-align: center;
    pointer-events: none;
}

.upload-icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-sm);
    opacity: 0.7;
}

.upload-content h3 {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-xs);
    color: var(--text-primary);
}

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

.upload-hint {
    color: var(--text-muted);
    font-size: 0.75rem;
    margin-top: var(--spacing-xs);
}

.preview-image {
    display: none;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: contain;
    padding: var(--spacing-md);
}

.upload-box.has-image .upload-content {
    display: none;
}

.upload-box.has-image .preview-image {
    display: block;
}

.remove-btn {
    display: none;
    position: absolute;
    top: var(--spacing-sm);
    right: var(--spacing-sm);
    width: 36px;
    height: 36px;
    background: rgba(239, 68, 68, 0.9);
    color: white;
    border: none;
    border-radius: 50%;
    font-size: 1.5rem;
    cursor: pointer;
    transition: var(--transition);
    z-index: 10;
}

.upload-box.has-image .remove-btn {
    display: flex;
    align-items: center;
    justify-content: center;
}

.remove-btn:hover {
    background: var(--danger);
    transform: scale(1.1);
}

/* Action Buttons */
.action-buttons {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

.btn {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-lg);
    border: none;
    border-radius: var(--radius-md);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    outline: none;
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    color: white;
    box-shadow: var(--shadow-md);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.1);
    color: var(--text-primary);
    border: 1px solid rgba(255, 255, 255, 0.2);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.15);
}

/* ===================================
   Results Section
   =================================== */
.results-section {
    animation: fadeIn 0.5s ease-in-out;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Score Card */
.score-card {
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.2), rgba(139, 92, 246, 0.2));
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    text-align: center;
    margin-bottom: var(--spacing-xl);
    backdrop-filter: blur(10px);
}

.score-value {
    font-size: clamp(3rem, 8vw, 5rem);
    font-weight: 800;
    background: linear-gradient(135deg, var(--primary-light), var(--secondary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-sm);
}

.score-label {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
}

.score-status {
    font-size: 1rem;
    font-weight: 600;
    padding: var(--spacing-xs) var(--spacing-md);
    border-radius: var(--radius-md);
    display: inline-block;
}

.score-status.perfect {
    background: rgba(16, 185, 129, 0.2);
    color: var(--success);
}

.score-status.excellent {
    background: rgba(34, 197, 94, 0.2);
    color: #22c55e;
}

.score-status.good {
    background: rgba(245, 158, 11, 0.2);
    color: var(--warning);
}

.score-status.different {
    background: rgba(239, 68, 68, 0.2);
    color: var(--danger);
}

/* Comparison Container */
.comparison-container {
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: var(--radius-lg);
    overflow: hidden;
    margin-bottom: var(--spacing-lg);
}

/* View Tabs */
.view-tabs {
    display: flex;
    background: rgba(0, 0, 0, 0.2);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

.view-tab {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-md);
    background: transparent;
    border: none;
    color: var(--text-secondary);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    position: relative;
}

.view-tab:hover {
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-primary);
}

.view-tab.active {
    color: var(--primary-light);
    background: rgba(99, 102, 241, 0.1);
}

.view-tab.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--primary), var(--secondary));
}

/* View Content */
.view-content {
    position: relative;
    min-height: 400px;
}

.view-panel {
    display: none;
    padding: var(--spacing-lg);
}

.view-panel.active {
    display: block;
}

/* Overlay View */
.overlay-container {
    position: relative;
    width: 100%;
    max-width: 800px;
    margin: 0 auto;
}

#overlayCanvas {
    width: 100%;
    height: auto;
    display: block;
    border-radius: var(--radius-md);
}

.slider-container {
    margin-top: var(--spacing-md);
}

.overlay-slider {
    width: 100%;
    height: 8px;
    border-radius: 4px;
    background: rgba(255, 255, 255, 0.1);
    outline: none;
    -webkit-appearance: none;
}

.overlay-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    cursor: pointer;
    box-shadow: var(--shadow-md);
}

.overlay-slider::-moz-range-thumb {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
    cursor: pointer;
    border: none;
    box-shadow: var(--shadow-md);
}

/* Side by Side View */
.side-by-side-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-lg);
}

.side-image {
    text-align: center;
}

.side-label {
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

#sideCanvas1,
#sideCanvas2 {
    width: 100%;
    height: auto;
    border-radius: var(--radius-md);
    border: 1px solid rgba(255, 255, 255, 0.1);
}

/* Difference View */
.difference-container {
    text-align: center;
}

#differenceCanvas {
    width: 100%;
    max-width: 800px;
    height: auto;
    border-radius: var(--radius-md);
    margin: 0 auto;
    display: block;
}

.difference-legend {
    display: flex;
    justify-content: center;
    gap: var(--spacing-lg);
    margin-top: var(--spacing-md);
    flex-wrap: wrap;
}

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

.legend-color {
    width: 20px;
    height: 20px;
    border-radius: 4px;
    border: 1px solid rgba(255, 255, 255, 0.2);
}

/* Export Actions */
.export-actions {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* ===================================
   Loading Overlay
   =================================== */
.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(15, 23, 42, 0.95);
    backdrop-filter: blur(10px);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.loading-spinner {
    width: 60px;
    height: 60px;
    border: 4px solid rgba(255, 255, 255, 0.1);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

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

.loading-text {
    margin-top: var(--spacing-md);
    font-size: 1.125rem;
    color: var(--text-secondary);
}

/* ===================================
   Footer
   =================================== */
.footer {
    background: rgba(15, 23, 42, 0.8);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    padding: var(--spacing-lg) 0;
    text-align: center;
    color: var(--text-muted);
}

.footer-stats {
    margin-top: var(--spacing-xs);
    font-size: 0.875rem;
}

/* ===================================
   Responsive Design
   =================================== */
@media (max-width: 768px) {
    .header-content {
        flex-direction: column;
        gap: var(--spacing-md);
    }
    
    .upload-grid {
        grid-template-columns: 1fr;
    }
    
    .view-tabs {
        flex-direction: column;
    }
    
    .view-tab.active::after {
        height: 100%;
        width: 3px;
        right: unset;
        top: 0;
        bottom: 0;
    }
    
    .action-buttons,
    .export-actions {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
        justify-content: center;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }
    
    .upload-box {
        min-height: 250px;
        padding: var(--spacing-md);
    }
}