/* ===== CSS Custom Properties ===== */
:root {
    --color-bg: #f4f6f9;
    --color-surface: #ffffff;
    --color-surface-hover: #f0f2f5;
    --color-primary: #2563eb;
    --color-primary-hover: #1d4ed8;
    --color-primary-light: #dbeafe;
    --color-text: #1e293b;
    --color-text-secondary: #64748b;
    --color-border: #e2e8f0;
    --color-success: #16a34a;
    --color-success-bg: #dcfce7;
    --color-error: #dc2626;
    --color-error-bg: #fee2e2;
    --color-warning: #f59e0b;
    --color-warning-bg: #fef3c7;
    --color-drop-zone-bg: #f8fafc;
    --color-drop-zone-border: #94a3b8;
    --color-drop-zone-active: #2563eb;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
    --radius: 12px;
    --radius-sm: 8px;
    --transition: 200ms ease;
}

@media (prefers-color-scheme: dark) {
    :root {
        --color-bg: #0f172a;
        --color-surface: #1e293b;
        --color-surface-hover: #334155;
        --color-primary: #3b82f6;
        --color-primary-hover: #60a5fa;
        --color-primary-light: #1e3a5f;
        --color-text: #f1f5f9;
        --color-text-secondary: #94a3b8;
        --color-border: #334155;
        --color-success: #22c55e;
        --color-success-bg: #14532d;
        --color-error: #ef4444;
        --color-error-bg: #7f1d1d;
        --color-warning: #fbbf24;
        --color-warning-bg: #78350f;
        --color-drop-zone-bg: #1e293b;
        --color-drop-zone-border: #475569;
        --color-drop-zone-active: #3b82f6;
        --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
        --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
        --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -4px rgba(0, 0, 0, 0.3);
    }
}

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

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ===== Header ===== */
.header {
    background-color: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    padding: 1rem 1.5rem;
    box-shadow: var(--shadow-sm);
}

.header-inner {
    max-width: 960px;
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem;
    flex-wrap: wrap;
}

.header-title {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-primary);
    letter-spacing: -0.02em;
}

.lang-selector {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.875rem;
    color: var(--color-text-secondary);
}

.lang-selector select {
    padding: 0.375rem 0.75rem;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    background-color: var(--color-surface);
    color: var(--color-text);
    font-size: 0.875rem;
    cursor: pointer;
    transition: border-color var(--transition);
}

.lang-selector select:hover {
    border-color: var(--color-primary);
}

.lang-selector select:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px var(--color-primary-light);
}

/* ===== Main ===== */
.main {
    flex: 1;
    max-width: 960px;
    width: 100%;
    margin: 0 auto;
    padding: 2rem 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.tagline {
    text-align: center;
    color: var(--color-text-secondary);
    font-size: 0.95rem;
}

/* ===== Drop Zone ===== */
.drop-zone {
    border: 2px dashed var(--color-drop-zone-border);
    border-radius: var(--radius);
    background-color: var(--color-drop-zone-bg);
    padding: 3rem 2rem;
    text-align: center;
    cursor: pointer;
    transition: border-color var(--transition), background-color var(--transition), transform var(--transition);
    position: relative;
}

.drop-zone:hover {
    border-color: var(--color-primary);
    background-color: var(--color-primary-light);
}

.drop-zone.drag-over {
    border-color: var(--color-drop-zone-active);
    background-color: var(--color-primary-light);
    transform: scale(1.01);
}

.drop-zone-icon {
    font-size: 3rem;
    margin-bottom: 0.75rem;
    display: block;
    opacity: 0.6;
}

.drop-zone-title {
    font-size: 1.125rem;
    font-weight: 600;
    margin-bottom: 0.25rem;
}

.drop-zone-subtitle {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    margin-bottom: 1rem;
}

.drop-zone input[type="file"] {
    display: none;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.625rem 1.25rem;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color var(--transition), transform var(--transition), box-shadow var(--transition);
    text-decoration: none;
}

.btn:active {
    transform: scale(0.98);
}

.btn-primary {
    background-color: var(--color-primary);
    color: #fff;
}

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

.btn-primary:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

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

.btn-success:hover {
    background-color: #15803d;
}

.btn-danger {
    background-color: var(--color-error);
    color: #fff;
}

.btn-danger:hover {
    background-color: #b91c1c;
}

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

.btn-outline:hover {
    background-color: var(--color-surface-hover);
    color: var(--color-text);
}

.btn-sm {
    padding: 0.375rem 0.75rem;
    font-size: 0.8125rem;
}

/* ===== File List Card ===== */
.file-list-card {
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    box-shadow: var(--shadow-md);
    overflow: hidden;
    display: none;
}

.file-list-card.visible {
    display: block;
}

.file-list-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 1.25rem;
    border-bottom: 1px solid var(--color-border);
    flex-wrap: wrap;
    gap: 0.5rem;
}

.file-list-header h2 {
    font-size: 1rem;
    font-weight: 600;
}

.file-list-meta {
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
}

.file-list {
    list-style: none;
    margin: 1.5rem 0;
    padding: 0;
}

.hidden {
    display: none !important;
}

.file-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem 1.25rem;
    border-bottom: 1px solid var(--color-border);
    transition: background-color var(--transition);
    position: relative;
}

.file-item:last-child {
    border-bottom: none;
}

.file-item:hover {
    background-color: var(--color-surface-hover);
}

.file-item-icon {
    width: 2.5rem;
    height: 2.5rem;
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1rem;
    flex-shrink: 0;
    background-color: var(--color-primary-light);
    color: var(--color-primary);
    position: relative;
    overflow: hidden;
    cursor: pointer;
}

.file-item-thumb {
    width: 100%;
    height: 100%;
    object-fit: cover;
    border-radius: 6px;
}

.file-item-preview {
    display: none;
    position: fixed;
    width: 220px;
    height: 220px;
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow-lg);
    border: 2px solid var(--color-border);
    background-color: var(--color-surface);
    object-fit: cover;
    z-index: 1000;
    pointer-events: none;
}

.file-item-info {
    flex: 1;
    min-width: 0;
}

.file-item-name {
    font-size: 0.875rem;
    font-weight: 500;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.file-item-size {
    font-size: 0.75rem;
    color: var(--color-text-secondary);
}

.file-item-status {
    font-size: 0.75rem;
    font-weight: 600;
    padding: 0.25rem 0.625rem;
    border-radius: 9999px;
    white-space: nowrap;
    flex-shrink: 0;
}

.status-pending {
    background-color: var(--color-warning-bg);
    color: var(--color-warning);
}

.status-converting {
    background-color: var(--color-primary-light);
    color: var(--color-primary);
}

.status-done {
    background-color: var(--color-success-bg);
    color: var(--color-success);
}

.status-error {
    background-color: var(--color-error-bg);
    color: var(--color-error);
}

.file-item-actions {
    flex-shrink: 0;
}

/* ===== Actions Bar ===== */
.actions-bar {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    padding: 1rem 1.25rem;
    border-top: 1px solid var(--color-border);
    flex-wrap: wrap;
}

/* ===== Overall Progress ===== */
.progress-container {
    display: none;
    padding: 0 1.25rem 1rem;
}

.progress-container.visible {
    display: block;
}

.progress-bar-wrapper {
    width: 100%;
    height: 6px;
    background-color: var(--color-border);
    border-radius: 3px;
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    background-color: var(--color-primary);
    border-radius: 3px;
    transition: width 300ms ease;
    width: 0%;
}

.progress-text {
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    margin-top: 0.5rem;
    text-align: center;
}

/* ===== Status Banner ===== */
.status-banner {
    display: none;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.25rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 500;
}

.status-banner.visible {
    display: flex;
}

.status-banner.success {
    background-color: var(--color-success-bg);
    color: var(--color-success);
}

.status-banner.error {
    background-color: var(--color-error-bg);
    color: var(--color-error);
}

/* ===== Footer ===== */
.footer {
    text-align: center;
    padding: 1.5rem;
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    border-top: 1px solid var(--color-border);
}

/* ===== Spinner ===== */
@keyframes spin {
    to { transform: rotate(360deg); }
}

.spinner {
    display: inline-block;
    width: 14px;
    height: 14px;
    border: 2px solid var(--color-border);
    border-top-color: var(--color-primary);
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
    vertical-align: middle;
}

/* ===== Modal ===== */
.modal-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: 1000;
    align-items: center;
    justify-content: center;
    padding: 1.5rem;
}

.modal-overlay.visible {
    display: flex;
}

.modal {
    background-color: var(--color-surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    padding: 2rem;
    max-width: 420px;
    width: 100%;
    text-align: center;
}

.modal-icon {
    font-size: 2.5rem;
    margin-bottom: 0.75rem;
}

.modal-title {
    font-size: 1.125rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.modal-message {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    margin-bottom: 1.5rem;
    line-height: 1.5;
}

.modal-actions {
    display: flex;
    gap: 0.75rem;
    justify-content: center;
}

.modal-actions .btn {
    min-width: 120px;
}

/* ===== Responsive ===== */
@media (max-width: 640px) {
    .header-inner {
        flex-direction: column;
        align-items: flex-start;
    }

    .drop-zone {
        padding: 2rem 1rem;
    }

    .file-item {
        flex-wrap: wrap;
    }

    .actions-bar {
        flex-direction: column;
    }

    .actions-bar .btn {
        width: 100%;
    }
}