/* CSS Variables (Expanded for consistency and light mode) */
:root {
    --font-primary: 'Montserrat', 'Arial', sans-serif;
    --font-secondary: 'Poppins', 'Helvetica', sans-serif;
    --bg-primary: #121212;
    --bg-secondary: #151515;
    --bg-tertiary: #171717;
    --text-primary: #d7d7d7;
    --text-secondary: #a0a0a0;
    --accent-primary: #edb049;
    --border-color: #2e2e2e;
    --spacing-xs: 5px;
    --spacing-sm: 10px;
    --spacing-md: 15px;
    --thumbnail-min-width: 250px; /* From resize-thumbnails.js */
}

/* Light Mode */
@media (prefers-color-scheme: light) {
    :root {
        --bg-primary: #f0f0f0;
        --bg-secondary: #e0e0e0;
        --bg-tertiary: #d0d0d0;
        --text-primary: #333;
        --text-secondary: #666;
        --accent-primary: #d48700;
        --border-color: #ccc;
    }
}

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

/* Scrollbar Styling (Cross-browser) */
html {
    scrollbar-width: thin; /* Firefox */
    -ms-overflow-style: none; /* IE and Edge */
}
html::-webkit-scrollbar {
    width: 8px; /* Chrome, Safari, Opera */
}
html::-webkit-scrollbar-track {
    background: var(--bg-secondary);
}
html::-webkit-scrollbar-thumb {
    background: var(--accent-primary);
    border-radius: 4px;
}

/* Body Styling */
html, body {
    width: 100%;
    height: 100%;
    overflow-x: hidden;
}

body {
    font-family: var(--font-primary);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    display: flex;
    flex-direction: column;
}

h1 {
    font-size: clamp(18px, 4vw, 20px); /* Fluid typography */
    margin-block-end: var(--spacing-xs);
    color: var(--text-primary);
}

h2 {
    font-size: clamp(14px, 3vw, 16px);
    color: var(--text-secondary);
    font-family: var(--font-secondary);
    font-weight: 400;
}

.main-container {
    display: flex;
    flex-direction: column;
    width: 100%;
    flex: 1;
    overflow-y: auto;
}

.top-container {
    flex: 0 0 auto;
    display: flex;
    flex-direction: column-reverse;
    justify-content: flex-end;
    align-items: center;
    padding-block-start: var(--spacing-sm);
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    border-block-end: 1px solid var(--border-color);
    transition: padding-block-start 0.3s ease;
}

.top-container.shrink {
    padding-block-start: var(--spacing-xs);
}

.navigation-buttons {
    display: flex;
    gap: 0.5rem;
    justify-content: center;
    padding-block-end: 0;
}

.nav-button {
    background-color: inherit;
    border: none;
    color: var(--text-secondary);
    font-family: var(--font-secondary);
    text-decoration: none;
    cursor: pointer;
    padding: var(--spacing-sm);
    inline-size: auto; /* Logical property */
    font-size: clamp(12px, 2.5vw, 14px);
    border-start-start-radius: 0.9em;
    border-start-end-radius: 0.9em;
    transition: background-color 0.5s ease, color 0.5s ease;
}

.nav-button:hover,
.nav-button.active {
    background-color: var(--bg-tertiary);
    color: var(--accent-primary);
}

.bottom-container {
    flex: 1;
    display: flex;
    justify-content: center;
    padding: var(--spacing-xs);
    background-color: var(--bg-secondary);
    border-radius: 5px;
    inline-size: 100%;
    margin-block-start: 0;
}

/* Thumbnail Container */
#thumbnail-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(var(--thumbnail-min-width), 1fr));
    gap: var(--spacing-sm);
    padding: var(--spacing-sm);
    transition: all 0.3s ease;
}

.thumbnail {
    position: relative;
    overflow: hidden;
    aspect-ratio: 4 / 3; /* Width/Height */
    opacity: 0;
    animation: fadeIn 0.5s ease forwards;
}

.thumbnail img {
    position: absolute;
    inset-block-start: 0; 
    inset-inline-start: 0;
    inline-size: 100%;
    block-size: 100%;
    object-fit: cover;
    transition: transform 0.3s ease; /* Smooth zoom transition */
}

.thumbnail:hover img {
    transform: scale(1.05); /* Zoom image on hover */
}

.thumbnail .thumbnail-title {
    position: absolute;
    inset-block-end: 0;
    inline-size: 100%;
    background: none;
    color: var(--text-secondary);
    padding: var(--spacing-md);
    text-align: center;
    font-size: clamp(16px, 2vw, 18px);
    white-space: normal; /* Allow wrapping */
    overflow: visible; /* Prevent clipping */
    line-height: 1.2; /* Better multi-line spacing */
}

.overlay-icon {
    position: absolute;
    inset-block-start: var(--spacing-sm);
    color: var(--accent-primary);
    font-size: clamp(14px, 2vw, 16px);
    inline-size: 20px;
    text-align: center;
}

.overlay-icon:nth-child(2) { inset-inline-start: 10px; }
.overlay-icon:nth-child(3) { inset-inline-start: 40px; }
.overlay-icon:nth-child(4) { inset-inline-start: 70px; }
.overlay-icon:nth-child(5) { inset-inline-start: 100px; }

/* Accessibility */
.sr-only {
    position: absolute;
    inline-size: 1px;
    block-size: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    border: 0;
}

#plus-button:focus,
#minus-button:focus {
    outline: 2px solid var(--accent-primary);
    outline-offset: 2px;
}

/* Motion Preference */
@media (prefers-reduced-motion: reduce) {
    #thumbnail-container,
    .top-container,
    .nav-button {
        transition: none;
    }
    .thumbnail {
        animation: none;
        opacity: 1;
    }
}

/* Responsive Design */
@media (max-width: 1024px) {
    #thumbnail-container {
        grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    }
}

@media (max-width: 768px) {
    #thumbnail-container {
        grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
    }
}

@media (max-width: 600px) {
    body {
        font-size: 14px;
    }
    h1, h2 {
        text-align: center;
    }
    .main-container {
        padding-block-start: var(--spacing-xs);
    }
    .top-container {
        padding-block-start: var(--spacing-xs);
    }
    .navigation-buttons {
        flex-direction: row;
        align-items: center;
        gap: 0.5rem;
    }
    .nav-button {
        inline-size: 100%;
        text-align: center;
    }
    .bottom-container {
        padding: 8px;
    }
    .thumbnail .overlay-icon {
        font-size: 14px;
        inline-size: 18px;
    }
}