:root {
    /* Colors - Pure White & Grayscale */
    --bg-body: #ffffff;
    --bg-surface: #ffffff;
    --bg-secondary: #f9fafb; /* Very light gray */
    --bg-hover: #f3f4f6;

    --text-primary: #111827; /* Near Black */
    --text-secondary: #4b5563; /* Dark Gray */
    --text-tertiary: #9ca3af; /* Light Gray */

    --border-light: #e5e7eb;
    --border-medium: #d1d5db;

    --accent-color: #2563eb; /* Restrained Blue for primary actions */
    --accent-hover: #1d4ed8;
    
    --danger-color: #ef4444;
    --success-color: #10b981;

    /* Typography */
    --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    --font-size-sm: 0.875rem;   /* 14px */
    --font-size-base: 1rem;      /* 16px */
    --font-size-lg: 1.125rem;    /* 18px */
    --font-size-xl: 1.5rem;      /* 24px */

    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;

    /* Borders & Radius */
    --radius-sm: 4px;
    --radius-md: 6px;
    --radius-lg: 8px;
    --radius-full: 9999px;

    /* Shadows (Restrained) */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-card: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06);
    --shadow-dropdown: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
}

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

body {
    font-family: var(--font-family);
    background-color: var(--bg-body);
    color: var(--text-primary);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

a {
    text-decoration: none;
    color: inherit;
    transition: color 0.2s ease;
}

button, input {
    font-family: inherit;
}

/* Navbar - Minimalist Top Bar */
.navbar {
    height: 64px;
    border-bottom: 1px solid var(--border-light);
    background-color: var(--bg-surface);
    position: sticky;
    top: 0;
    z-index: 100;
    display: flex;
    justify-content: center;
}

.nav-container {
    width: 100%;
    max-width: 1200px;
    padding: 0 var(--spacing-lg);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    font-weight: 600;
    font-size: 1.25rem;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.nav-menu {
    display: flex;
    gap: var(--spacing-xl);
}

.nav-item {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
    font-weight: 500;
    padding: var(--spacing-xs) 0;
    position: relative;
}

.nav-item:hover, .nav-item.active {
    color: var(--text-primary);
}

.nav-item.active::after {
    content: '';
    position: absolute;
    bottom: -21px; /* Align with navbar border */
    left: 0;
    width: 100%;
    height: 2px;
    background-color: var(--text-primary);
}

.nav-toggle {
    display: none;
    cursor: pointer;
    font-size: 1.25rem;
    color: var(--text-secondary);
}

/* Layout */
.main-content {
    flex: 1;
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-xl) var(--spacing-lg);
}

.container {
    width: 100%;
}

/* Typography Helpers */
h1 {
    font-size: var(--font-size-xl);
    font-weight: 600;
    margin-bottom: var(--spacing-lg);
    color: var(--text-primary);
}

.text-muted {
    color: var(--text-tertiary);
}

/* Upload Area - Dashed Card */
.upload-container {
    margin-bottom: var(--spacing-xl);
}

.upload-area-dashed {
    border: 2px dashed var(--border-medium);
    border-radius: var(--radius-lg);
    background-color: var(--bg-secondary);
    padding: var(--spacing-xl);
    text-align: center;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-md);
}

.upload-area-dashed:hover, .upload-area-dashed.active {
    border-color: var(--accent-color);
    background-color: #f0f7ff; /* Very subtle blue tint */
}

.upload-area-dashed i {
    font-size: 2rem;
    color: var(--text-tertiary);
    transition: color 0.2s ease;
}

.upload-area-dashed p {
    color: var(--text-secondary);
    font-size: var(--font-size-base);
}

.upload-area-dashed span {
    color: var(--accent-color);
    font-weight: 500;
}

/* Progress & Upload List */
.progress-area, .done-area {
    margin-top: var(--spacing-md);
}

.upload-row {
    background-color: var(--bg-surface);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-md);
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
    display: flex;
    align-items: center;
    justify-content: space-between;
    box-shadow: var(--shadow-sm);
}

.upload-row .content {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    flex: 1;
    overflow: hidden;
}

.upload-row .details {
    display: flex;
    flex-direction: column;
    flex: 1;
    min-width: 0;
}

.upload-row .name {
    font-weight: 500;
    font-size: var(--font-size-sm);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.upload-row .status {
    font-size: 0.75rem;
    color: var(--text-tertiary);
}

.upload-row .status a {
    color: var(--accent-color);
}

.progress-bar {
    height: 4px;
    background-color: var(--bg-secondary);
    border-radius: var(--radius-full);
    width: 100%;
    margin-top: var(--spacing-xs);
    overflow: hidden;
}

.progress-bar .progress {
    height: 100%;
    background-color: var(--accent-color);
    width: 0;
    transition: width 0.3s ease;
}

/* Controls Bar (Search & Batch Actions) */
.controls-bar {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-md);
    padding-bottom: var(--spacing-md);
    border-bottom: 1px solid var(--border-light);
}

.search-container {
    position: relative;
    width: 300px;
    max-width: 100%;
}

.search-input {
    width: 100%;
    padding: var(--spacing-sm) var(--spacing-md) var(--spacing-sm) 36px;
    border: 1px solid var(--border-medium);
    border-radius: var(--radius-md);
    font-size: var(--font-size-sm);
    background-color: var(--bg-surface);
    transition: border-color 0.2s ease;
}

.search-input:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 2px rgba(37, 99, 235, 0.1);
}

.search-icon {
    position: absolute;
    left: 12px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-tertiary);
    font-size: var(--font-size-sm);
}

.batch-actions {
    display: flex;
    gap: var(--spacing-sm);
    align-items: center;
}

.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-md);
    font-size: var(--font-size-sm);
    font-weight: 500;
    cursor: pointer;
    border: 1px solid transparent;
    transition: all 0.2s ease;
    background-color: var(--bg-surface);
    color: var(--text-secondary);
    border-color: var(--border-medium);
}

.btn:hover:not(:disabled) {
    background-color: var(--bg-hover);
    color: var(--text-primary);
}

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

.btn-primary {
    background-color: var(--accent-color);
    color: white;
    border-color: transparent;
}

.btn-primary:hover:not(:disabled) {
    background-color: var(--accent-hover);
    color: white;
}

.btn-danger {
    color: var(--danger-color);
    border-color: var(--border-medium);
}

.btn-danger:hover:not(:disabled) {
    background-color: #fef2f2;
    border-color: #fca5a5;
}

/* File List - Table Style */
.file-list-header {
    display: grid;
    grid-template-columns: 40px minmax(0, 3fr) 120px 150px 140px;
    gap: var(--spacing-md);
    padding: var(--spacing-sm) var(--spacing-lg);
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border-light);
}

.file-list {
    display: flex;
    flex-direction: column;
}

.file-item {
    display: grid;
    grid-template-columns: 40px minmax(0, 3fr) 120px 150px 140px;
    gap: var(--spacing-md);
    padding: var(--spacing-md) var(--spacing-lg);
    align-items: center;
    border-bottom: 1px solid var(--border-light);
    transition: background-color 0.1s ease;
    font-size: var(--font-size-sm);
}

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

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

.col-checkbox {
    display: flex;
    justify-content: center;
}

.col-name {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    overflow: hidden;
}

.col-name i {
    font-size: 1.25rem;
    color: var(--text-secondary);
}

.col-name span {
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    font-weight: 500;
    color: var(--text-primary);
}

.col-size, .col-date {
    color: var(--text-secondary);
}

.col-actions {
    display: flex;
    justify-content: flex-end;
    gap: var(--spacing-xs);
    opacity: 0;
    transition: opacity 0.2s ease;
}

.file-item:hover .col-actions {
    opacity: 1;
}

.action-btn {
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-sm);
    border: none;
    background: transparent;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.2s ease;
    position: relative; /* For tooltip */
}

.action-btn:hover {
    background-color: var(--bg-secondary);
    color: var(--text-primary);
}

.action-btn.delete:hover {
    color: var(--danger-color);
    background-color: #fef2f2;
}

/* Tooltip implementation via CSS */
.action-btn[data-tooltip]::before {
    content: attr(data-tooltip);
    position: absolute;
    bottom: 100%;
    left: 50%;
    transform: translateX(-50%);
    padding: 4px 8px;
    background-color: var(--text-primary);
    color: white;
    font-size: 0.75rem;
    border-radius: var(--radius-sm);
    white-space: nowrap;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.2s ease;
    margin-bottom: 4px;
    z-index: 10;
}

.action-btn:hover::before {
    opacity: 1;
}

/* Image Hosting Grid */
.image-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: var(--spacing-lg);
}

.image-card {
    background-color: var(--bg-surface);
    border: 1px solid var(--border-light);
    border-radius: var(--radius-lg);
    overflow: hidden;
    transition: all 0.2s ease;
    display: flex;
    flex-direction: column;
}

.image-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-card);
    border-color: var(--border-medium);
}

.image-thumb-wrapper {
    aspect-ratio: 16/9;
    overflow: hidden;
    background-color: var(--bg-secondary);
    position: relative;
}

.image-thumb {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.3s ease;
}

.image-card:hover .image-thumb {
    transform: scale(1.05);
}

.image-info {
    padding: var(--spacing-md);
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.image-name {
    font-size: var(--font-size-sm);
    font-weight: 500;
    color: var(--text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.image-meta {
    font-size: 0.75rem;
    color: var(--text-tertiary);
}

.image-actions {
    padding: var(--spacing-sm) var(--spacing-md);
    border-top: 1px solid var(--border-light);
    display: flex;
    justify-content: flex-end;
    gap: var(--spacing-xs);
    background-color: var(--bg-secondary);
}

/* Toast */
.toast {
    position: fixed;
    bottom: 24px;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    background-color: var(--text-primary);
    color: white;
    padding: 10px 20px;
    border-radius: var(--radius-full);
    box-shadow: var(--shadow-dropdown);
    font-size: var(--font-size-sm);
    opacity: 0;
    transition: all 0.3s cubic-bezier(0.68, -0.55, 0.27, 1.55);
    z-index: 1000;
}

.toast.show {
    transform: translateX(-50%) translateY(0);
    opacity: 1;
}

.toast.error {
    background-color: var(--danger-color);
}

/* Checkbox */
input[type="checkbox"] {
    width: 16px;
    height: 16px;
    accent-color: var(--accent-color);
    cursor: pointer;
}

/* Responsive */
@media (max-width: 768px) {
    .nav-menu {
        display: none; /* Mobile menu logic to be implemented or simplified */
    }
    .nav-toggle {
        display: block;
    }
    
    .file-list-header {
        display: none;
    }

    .file-item {
        grid-template-columns: 40px 1fr;
        gap: var(--spacing-sm);
        padding: var(--spacing-md);
    }

    .col-checkbox {
        grid-row: 1 / 3;
    }

    .col-name {
        grid-column: 2;
    }

    .col-size, .col-date {
        display: none; /* Simplify for mobile */
    }
    
    .col-actions {
        grid-column: 2;
        justify-content: flex-start;
        opacity: 1;
    }

    .controls-bar {
        flex-direction: column;
        align-items: stretch;
    }

    .search-container {
        width: 100%;
    }
}