/* CSS_VERSION: 0.1.2 */
/* LLM/FUTURE MAINTAINER: Current app version is 0.1.2. Keep this CSS_VERSION, the HTML asset query strings/version badge, APP_VERSION/JS_VERSION in app.js, and sw.js CACHE_NAME/static asset URLs in sync for every release. */

/* ========================================
   Google Fonts Import
   ======================================== */
@import url('https://fonts.googleapis.com/css2?family=Sora:wght@400;500;600;700&family=DM+Sans:wght@400;500;600&display=swap');

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

:root {
    /* Colors - Modern & Vibrant */
    --color-primary: #6366f1;
    --color-primary-hover: #4f46e5;
    --color-primary-active: #4338ca;
    --color-primary-light: #eef2ff;
    --color-secondary: #64748b;
    --color-success: #10b981;
    --color-error: #ef4444;
    --color-warning: #f59e0b;

    /* Neutral */
    --color-bg: #f8fafc;
    --color-surface: #ffffff;
    --color-border: #f1f5f9;
    --color-border-hover: #e2e8f0;
    --color-text: #0f172a;
    --color-text-secondary: #475569;
    --color-text-muted: #94a3b8;

    /* Upload zone */
    --color-upload-border: #cbd5e1;
    --color-upload-bg: #ffffff;
    --color-upload-drag: #f5f3ff;
    --color-upload-drag-border: #6366f1;

    /* Shadows - Refined */
    --shadow-sm: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
    --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);
    --shadow-indigo: 0 10px 15px -3px rgba(99, 102, 241, 0.2), 0 4px 6px -4px rgba(99, 102, 241, 0.1);

    /* Typography */
    --font-heading: 'Sora', system-ui, sans-serif;
    --font-body: 'DM Sans', system-ui, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.8125rem;
    --font-size-base: 0.9375rem;
    --font-size-lg: 1.0625rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;

    /* 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;

    /* Borders */
    --radius-sm: 0.375rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    --radius-2xl: 1.25rem;

    /* Transitions */
    --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 400ms cubic-bezier(0.4, 0, 0.2, 1);
    --transition-spring: 500ms cubic-bezier(0.34, 1.56, 0.64, 1);
}

html {
    font-size: 16px;
    -webkit-text-size-adjust: 100%;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-body);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--color-text);
    background: var(--color-bg);
    min-height: 100vh;
    min-height: 100dvh;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Reduced motion */
@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(--color-primary);
    outline-offset: 2px;
    border-radius: 4px;
}

/* Selection */
::selection {
    background-color: var(--color-primary);
    color: white;
}

/* ========================================
   App Container
   ======================================== */
.app-container {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    min-height: 100dvh;
    background:
        radial-gradient(circle at 0% 0%, rgba(99, 102, 241, 0.05) 0%, transparent 50%),
        radial-gradient(circle at 100% 100%, rgba(99, 102, 241, 0.05) 0%, transparent 50%),
        var(--color-bg);
}

/* ========================================
   Header
   ======================================== */
.header {
    background: rgba(255, 255, 255, 0.7);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--color-border);
    padding: var(--space-4) var(--space-6);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    max-width: 1400px;
    margin: 0 auto;
}

.logo-section {
    display: flex;
    align-items: center;
    gap: var(--space-3);
}

.logo-icon {
    width: 36px;
    height: 36px;
    color: var(--color-primary);
    flex-shrink: 0;
    filter: drop-shadow(0 2px 4px rgba(79, 70, 229, 0.2));
}

.product-name {
    font-family: var(--font-heading);
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--color-text);
    letter-spacing: -0.02em;
}

.version-badge {
    font-family: var(--font-body);
    font-size: var(--font-size-xs);
    font-weight: 500;
    color: var(--color-text-muted);
    background: var(--color-bg);
    padding: var(--space-1) var(--space-2);
    border-radius: 20px;
    border: 1px solid var(--color-border);
    letter-spacing: 0.02em;
}

/* ========================================
   Main Content
   ======================================== */
.main-content {
    flex: 1;
    padding: var(--space-6);
    max-width: 1400px;
    margin: 0 auto;
    width: 100%;
}

.converter-layout {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-5);
    height: 100%;
}

/* ========================================
   Upload Panel
   ======================================== */
.upload-panel {
    display: flex;
    flex-direction: column;
    gap: var(--space-4);
}

.upload-zone {
    position: relative;
    border: 2.5px dashed var(--color-upload-border);
    border-radius: 32px;
    background: var(--color-upload-bg);
    padding: 64px 32px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    user-select: none;
    -webkit-user-select: none;
    box-shadow: inset 0 2px 4px 0 rgb(0 0 0 / 0.05);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    width: 100%;
}

.upload-zone:hover {
    border-color: var(--color-primary);
    background: #ffffff;
    box-shadow: 0 12px 24px -8px rgba(99, 102, 241, 0.15);
    transform: translateY(-2px);
}

.upload-zone.dragover {
    border-color: var(--color-upload-drag-border);
    border-style: solid;
    background: var(--color-upload-drag);
    transform: scale(1.01);
    box-shadow: var(--shadow-indigo);
}

.upload-zone-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    width: 100%;
    position: relative;
    z-index: 1;
}

.upload-icon-wrapper {
    width: 80px;
    height: 80px;
    border-radius: 24px;
    background: var(--color-primary-light);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 24px;
    transition: all 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
    color: var(--color-primary);
    flex-shrink: 0;
}

.upload-zone:hover .upload-icon-wrapper {
    background: var(--color-primary);
    color: #ffffff !important;
    transform: scale(1.1);
    box-shadow: 0 8px 16px -4px rgba(99, 102, 241, 0.4);
}

.upload-icon {
    width: 36px;
    height: 36px;
    color: inherit;
    transition: transform 0.4s ease;
}

.upload-zone:hover .upload-icon {
    transform: scale(1.1);
    color: #ffffff !important;
}

.upload-text-primary {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--color-text);
    margin: 0 0 8px 0;
    line-height: 1.2;
    letter-spacing: -0.02em;
}

.upload-text-secondary {
    font-size: 1rem;
    color: var(--color-text-secondary);
    margin: 0;
    line-height: 1.4;
    font-weight: 500;
}

.upload-formats {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    margin-top: 24px;
}

.upload-formats span {
    font-size: 10px;
    font-weight: 700;
    color: var(--color-text-secondary);
    padding: 2px 8px;
    background: var(--color-bg);
    border: 1px solid var(--color-border-hover);
    border-radius: 6px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.file-input {
    display: none;
}

/* Image Count */
.image-count {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-4);
    padding: var(--space-5) var(--space-6);
    background: var(--color-surface);
    border-radius: var(--radius-xl);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-sm);
}

.count-label {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
    font-weight: 500;
}

.count-value {
    font-family: var(--font-heading);
    font-size: var(--font-size-xl);
    font-weight: 800;
    color: var(--color-primary);
    letter-spacing: -0.03em;
}

/* ========================================
   Controls
   ======================================== */
.controls {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: var(--space-4);
}

.controls .btn-primary {
    grid-column: 1 / -1;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-3);
    padding: var(--space-4) var(--space-6);
    font-family: var(--font-body);
    font-size: var(--font-size-base);
    font-weight: 600;
    line-height: 1;
    border-radius: var(--radius-xl);
    border: none;
    cursor: pointer;
    transition: all var(--transition-fast);
    user-select: none;
    -webkit-user-select: none;
    width: 100%;
    min-width: 0;
    min-height: 52px;
    letter-spacing: 0.01em;
}

[hidden] {
    display: none !important;
}

.btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
    transform: none !important;
}

.btn-icon {
    width: 22px;
    height: 22px;
    flex-shrink: 0;
}

.btn-primary {
    background: var(--color-primary);
    color: white;
    box-shadow: var(--shadow-indigo);
}

.btn-primary:hover:not(:disabled) {
    background: var(--color-primary-hover);
    box-shadow: var(--shadow-lg);
    transform: translateY(-2px);
}

.btn-primary:active:not(:disabled) {
    transform: translateY(0);
}

.btn-secondary {
    background: var(--color-surface);
    color: var(--color-text-secondary);
    border: 1px solid var(--color-border-hover);
}

.btn-secondary:hover:not(:disabled) {
    background: var(--color-bg);
    color: var(--color-text);
    border-color: var(--color-primary-light);
    transform: translateY(-1px);
}

.btn-secondary:active:not(:disabled) {
    transform: translateY(0);
    background: var(--color-border);
}

.btn-download {
    color: var(--color-primary);
}

/* ========================================
   Utility Classes
   ======================================== */
.hidden {
    display: none !important;
}

/* ========================================
   Status Region
   ======================================== */
.status-region {
    min-height: 0;
    padding: 0;
    border-radius: var(--radius-xl);
    font-size: var(--font-size-sm);
    font-weight: 500;
    text-align: center;
    opacity: 0;
    transform: translateY(-8px);
    transition: all var(--transition-base);
    overflow: hidden;
}

.status-region.visible {
    min-height: 48px;
    padding: var(--space-3) var(--space-4);
    opacity: 1;
    transform: translateY(0);
}

.status-region.success {
    background: #f0fdf4;
    color: #166534;
    border: 1px solid #bbf7d0;
}

.status-region.error {
    background: #fef2f2;
    color: #991b1b;
    border: 1px solid #fecaca;
}

.status-region.info {
    background: #f0f9ff;
    color: #075985;
    border: 1px solid #bae6fd;
}

/* ========================================
   Preview Panel
   ======================================== */
.preview-panel {
    background: var(--color-surface);
    border-radius: var(--radius-2xl);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-md);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    min-height: 400px;
    transition: box-shadow var(--transition-base);
}

.preview-panel:hover {
    box-shadow: var(--shadow-lg);
}

.preview-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-4) var(--space-6);
    border-bottom: 1px solid var(--color-border);
    background: var(--color-surface);
}

.preview-title {
    font-family: var(--font-heading);
    font-size: var(--font-size-base);
    font-weight: 600;
    color: var(--color-text);
    display: flex;
    align-items: center;
    gap: var(--space-2);
}

.preview-count {
    font-family: var(--font-body);
    font-size: var(--font-size-xs);
    font-weight: 500;
    color: var(--color-text-muted);
    background: var(--color-bg);
    padding: var(--space-1) var(--space-3);
    border-radius: 20px;
    border: 1px solid var(--color-border);
}

.thumbnail-grid {
    flex: 1;
    padding: var(--space-4);
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: var(--space-4);
    align-content: start;
    overflow-y: auto;
    scrollbar-width: thin;
    scrollbar-color: var(--color-border-hover) transparent;
}

.thumbnail-grid::-webkit-scrollbar {
    width: 6px;
}

.thumbnail-grid::-webkit-scrollbar-track {
    background: transparent;
}

.thumbnail-grid::-webkit-scrollbar-thumb {
    background: var(--color-border-hover);
    border-radius: 3px;
}

.thumbnail-grid::-webkit-scrollbar-thumb:hover {
    background: var(--color-text-muted);
}

/* Empty Preview State */
.empty-preview {
    grid-column: 1 / -1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--space-10);
    color: var(--color-text-muted);
    text-align: center;
    animation: fadeIn 0.4s ease-out;
}

.empty-icon-wrapper {
    width: 80px;
    height: 80px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--color-bg) 0%, #e5e7eb 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: var(--space-4);
}

.empty-icon {
    width: 36px;
    height: 36px;
    color: var(--color-text-muted);
    opacity: 0.6;
}

.empty-text {
    font-family: var(--font-heading);
    font-size: var(--font-size-base);
    font-weight: 500;
    color: var(--color-text-secondary);
    margin-bottom: var(--space-1);
}

.empty-hint {
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

/* ========================================
   Thumbnail Item
   ======================================== */
.thumbnail {
    position: relative;
    aspect-ratio: 1;
    border-radius: var(--radius-xl);
    overflow: hidden;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-base);
    animation: thumbnailEnter 0.4s cubic-bezier(0.34, 1.56, 0.64, 1) backwards;
}

.thumbnail:hover {
    transform: translateY(-4px) scale(1.02);
    box-shadow: var(--shadow-xl);
    border-color: var(--color-primary-light);
    z-index: 10;
}

.thumbnail img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
    transition: transform var(--transition-base);
}

.thumbnail:hover img {
    transform: scale(1.08);
}

/* Remove Button */
.thumbnail-remove {
    position: absolute;
    top: var(--space-2);
    right: var(--space-2);
    width: 28px;
    height: 28px;
    border-radius: 8px;
    border: none;
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(4px);
    color: var(--color-error);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transform: scale(0.8);
    transition: all var(--transition-base);
    box-shadow: var(--shadow-sm);
    z-index: 5;
}

.thumbnail:hover .thumbnail-remove {
    opacity: 1;
    transform: scale(1);
}

.thumbnail-remove:hover {
    background: var(--color-error);
    color: white;
}

.thumbnail-remove svg {
    width: 14px;
    height: 14px;
}

/* Filename Badge */
.thumbnail-filename {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    padding: var(--space-3) var(--space-2);
    background: linear-gradient(transparent, rgba(15, 23, 42, 0.8));
    color: white;
    font-size: 10px;
    font-weight: 500;
    text-overflow: ellipsis;
    white-space: nowrap;
    overflow: hidden;
    opacity: 0;
    transform: translateY(100%);
    transition: all var(--transition-base);
}

.thumbnail:hover .thumbnail-filename {
    opacity: 1;
    transform: translateY(0);
}

/* Image Number Badge */
.thumbnail-number {
    position: absolute;
    top: var(--space-2);
    left: var(--space-2);
    width: 24px;
    height: 24px;
    border-radius: 8px;
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(4px);
    color: var(--color-primary);
    font-size: 11px;
    font-weight: 700;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-sm);
    z-index: 5;
}

/* ========================================
   Footer
   ======================================== */
.footer {
    padding: var(--space-5) var(--space-6);
    text-align: center;
    border-top: 1px solid rgba(229, 231, 235, 0.6);
    background: rgba(255, 255, 255, 0.6);
    backdrop-filter: blur(8px);
}

.footer-content {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    max-width: 1400px;
    margin: 0 auto;
}

.lock-icon {
    width: 20px;
    height: 20px;
    color: var(--color-success);
    flex-shrink: 0;
}

.privacy-note {
    font-size: var(--font-size-sm);
    color: var(--color-text-secondary);
}

/* ========================================
   Loading Overlay
   ======================================== */
.loading-overlay {
    position: fixed;
    inset: 0;
    background: rgba(17, 24, 39, 0.8);
    backdrop-filter: blur(8px);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: var(--space-5);
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition:
        opacity var(--transition-base),
        visibility var(--transition-base);
}

.loading-overlay:not([hidden]) {
    opacity: 1;
    visibility: visible;
}

.loading-spinner {
    width: 56px;
    height: 56px;
    color: white;
    filter: drop-shadow(0 4px 12px rgba(79, 70, 229, 0.4));
}

.loading-spinner svg {
    width: 100%;
    height: 100%;
    animation: spin 1.2s cubic-bezier(0.4, 0, 0.2, 1) infinite;
}

@keyframes spin {
    0% {
        transform: rotate(0deg);
    }
    100% {
        transform: rotate(360deg);
    }
}

.loading-text {
    color: white;
    font-family: var(--font-heading);
    font-size: var(--font-size-lg);
    font-weight: 600;
    letter-spacing: 0.01em;
}

/* Progress bar in loading */
.loading-progress {
    width: 200px;
    height: 4px;
    background: rgba(255, 255, 255, 0.2);
    border-radius: 2px;
    overflow: hidden;
}

.loading-progress-bar {
    height: 100%;
    background: linear-gradient(90deg, var(--color-primary), #a78bfa);
    border-radius: 2px;
    transition: width var(--transition-base);
    width: 0%;
}

/* ========================================
   Animations
   ======================================== */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(8px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes pulse {
    0%, 100% {
        opacity: 1;
    }
    50% {
        opacity: 0.6;
    }
}

/* ========================================
   Desktop Layout (min-width: 768px)
   ======================================== */
@media (min-width: 768px) {
    .header {
        padding: var(--space-4) var(--space-10);
    }

    .main-content {
        padding: var(--space-8) var(--space-10);
    }

    .converter-layout {
        grid-template-columns: 400px 1fr;
        gap: var(--space-10);
    }

    .upload-panel {
        gap: var(--space-8);
    }

    .upload-zone {
        padding: 80px 48px;
    }

    .preview-panel {
        min-height: 700px;
    }

    .thumbnail-grid {
        grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
        gap: var(--space-6);
        padding: var(--space-6);
    }

    .controls {
        grid-template-columns: 1fr;
    }

    .controls .btn-primary,
    .btn {
        grid-column: auto;
        min-width: unset;
        padding: var(--space-4) var(--space-6);
    }

    .footer {
        padding: var(--space-6) var(--space-10);
    }
}

/* ========================================
   Large Desktop (min-width: 1024px)
   ======================================== */
@media (min-width: 1024px) {
    .converter-layout {
        grid-template-columns: 420px 1fr;
    }

    .thumbnail-grid {
        grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
    }
}

/* ========================================
   Print Styles
   ======================================== */
@media print {
    .header,
    .footer,
    .controls,
    .upload-zone,
    .thumbnail-remove,
    .loading-overlay,
    .thumbnail-number {
        display: none !important;
    }

    .app-container {
        display: block;
    }

    .main-content {
        padding: 0;
        max-width: none;
    }

    .preview-panel {
        border: none;
        background: none;
        box-shadow: none;
    }

    .thumbnail-grid {
        display: flex;
        flex-wrap: wrap;
        gap: var(--space-4);
    }

    .thumbnail {
        width: 180px;
        height: 180px;
    }
}