/* CSS Variables */
:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --secondary-color: #64748b;
    --secondary-hover: #475569;
    --success-color: #10b981;
    --success-hover: #059669;
    --background: #0f172a;
    --surface: #1e293b;
    --surface-hover: #334155;
    --border: #334155;
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -2px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -4px rgba(0, 0, 0, 0.2);
    --radius: 12px;
    --radius-sm: 8px;
    --transition: 0.2s ease;
}

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

/* Base */
html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* App Container */
.app-container {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem;
}

/* Header */
.header {
    text-align: center;
    padding: 2rem 1rem;
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    margin-bottom: 0.5rem;
}

.logo svg {
    width: 2.5rem;
    height: 2.5rem;
    color: var(--primary-color);
}

.logo h1 {
    font-size: 1.75rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary-color), #a855f7);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

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

/* Main Content */
.main-content {
    flex: 1;
    position: relative;
}

/* Upload Section */
.upload-section {
    padding: 1rem;
}

.upload-area {
    border: 2px dashed var(--border);
    border-radius: var(--radius);
    padding: 3rem 2rem;
    text-align: center;
    cursor: pointer;
    transition: all var(--transition);
    background: var(--surface);
}

.upload-area:hover,
.upload-area.dragover {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
}

.upload-icon {
    width: 4rem;
    height: 4rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.upload-text {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.upload-subtext {
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

.upload-formats {
    font-size: 0.875rem;
    color: var(--text-muted);
}

/* Controls Section */
.controls-section {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 1.5rem;
    margin: 1rem;
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.control-group label {
    font-weight: 500;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.slider-container {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.slider-container input[type="range"] {
    flex: 1;
    height: 6px;
    border-radius: 3px;
    background: var(--border);
    -webkit-appearance: none;
    appearance: none;
    cursor: pointer;
}

.slider-container input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
    transition: transform var(--transition);
}

.slider-container input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.1);
}

.slider-container input[type="range"]::-moz-range-thumb {
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
    border: none;
}

.slider-value {
    min-width: 2.5rem;
    text-align: center;
    font-weight: 600;
    color: var(--primary-color);
    font-size: 1.125rem;
}

select {
    width: 100%;
    padding: 0.75rem 1rem;
    border-radius: var(--radius-sm);
    border: 1px solid var(--border);
    background: var(--background);
    color: var(--text-primary);
    font-size: 1rem;
    cursor: pointer;
    transition: border-color var(--transition);
}

select:hover,
select:focus {
    border-color: var(--primary-color);
    outline: none;
}

/* Buttons */
.button-group {
    display: flex;
    gap: 0.75rem;
    margin-top: 0.5rem;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-sm);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition);
    border: none;
    text-decoration: none;
}

.btn svg {
    width: 1.25rem;
    height: 1.25rem;
}

.btn-primary {
    flex: 1;
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-hover);
}

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

.btn-secondary:hover {
    background: var(--secondary-hover);
}

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

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

.btn-outline {
    background: transparent;
    border: 2px solid var(--border);
    color: var(--text-primary);
}

.btn-outline:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

/* Preview Section */
.preview-section {
    padding: 1rem;
}

.preview-container {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.5rem;
    margin-bottom: 1.5rem;
}

@media (min-width: 768px) {
    .preview-container {
        grid-template-columns: 1fr 1fr;
    }
}

.preview-panel {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 1rem;
    overflow: hidden;
}

.preview-panel h3 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.image-wrapper {
    display: flex;
    justify-content: center;
    align-items: center;
    background: var(--background);
    border-radius: var(--radius-sm);
    overflow: hidden;
    min-height: 200px;
}

.image-wrapper canvas {
    max-width: 100%;
    max-height: 400px;
    object-fit: contain;
}

.image-info {
    font-size: 0.75rem;
    color: var(--text-muted);
    text-align: center;
    margin-top: 0.5rem;
}

/* Palette Section */
.palette-section {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 1rem;
    margin-bottom: 1.5rem;
}

.palette-section h3 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 0.75rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.palette {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.palette-color {
    width: 2.5rem;
    height: 2.5rem;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: transform var(--transition);
    border: 2px solid transparent;
    position: relative;
}

.palette-color:hover {
    transform: scale(1.1);
    border-color: white;
}

.palette-color::after {
    content: attr(data-hex);
    position: absolute;
    bottom: calc(100% + 4px);
    left: 50%;
    transform: translateX(-50%);
    background: var(--background);
    color: var(--text-primary);
    padding: 0.25rem 0.5rem;
    border-radius: 4px;
    font-size: 0.625rem;
    font-family: monospace;
    white-space: nowrap;
    opacity: 0;
    pointer-events: none;
    transition: opacity var(--transition);
    z-index: 10;
}

.palette-color:hover::after {
    opacity: 1;
}

/* Download Section */
.download-section {
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    justify-content: center;
}

.download-section .btn {
    min-width: 160px;
}

/* Loading Overlay */
.loading-overlay {
    position: absolute;
    inset: 0;
    background: rgba(15, 23, 42, 0.9);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    z-index: 100;
    border-radius: var(--radius);
}

.loading-spinner {
    width: 48px;
    height: 48px;
    border: 4px solid var(--border);
    border-top-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

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

/* Footer */
.footer {
    text-align: center;
    padding: 2rem 1rem;
    margin-top: auto;
    border-top: 1px solid var(--border);
}

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

.footer a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition);
}

.footer a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

/* Hidden attribute */
[hidden] {
    display: none !important;
}

/* Mobile Responsive */
@media (max-width: 640px) {
    .app-container {
        padding: 0.5rem;
    }

    .header {
        padding: 1.5rem 0.5rem;
    }

    .logo h1 {
        font-size: 1.5rem;
    }

    .logo svg {
        width: 2rem;
        height: 2rem;
    }

    .upload-area {
        padding: 2rem 1rem;
    }

    .upload-icon {
        width: 3rem;
        height: 3rem;
    }

    .upload-text {
        font-size: 1rem;
    }

    .controls-section {
        margin: 0.5rem;
        padding: 1rem;
    }

    .preview-section {
        padding: 0.5rem;
    }

    .button-group {
        flex-direction: column;
    }

    .download-section {
        flex-direction: column;
    }

    .download-section .btn {
        width: 100%;
    }

    .palette-color {
        width: 2rem;
        height: 2rem;
    }
}

/* Touch device optimizations */
@media (hover: none) {
    .palette-color:hover {
        transform: none;
    }

    .palette-color::after {
        display: none;
    }
}

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

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

button:focus-visible,
select:focus-visible,
input:focus-visible {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}