@import url('https://fonts.googleapis.com/css2?family=IBM+Plex+Mono:ital,wght@0,300;0,400;0,500;0,600;0,700;1,400&display=swap');

:root {
    --color-bg: #fbfbfb;
    --color-text: #222222;
    --color-text-muted: #595959;
    --color-border: #e2e8f0;
    --color-accent: #dd5522;
    --color-code-bg: #f6f8fa;
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-mono: "IBM Plex Mono", Courier, monospace;
}

@media (prefers-color-scheme: dark) {
    :root {
        --color-bg: #16161a;
        --color-text: #cdd6f4;
        --color-text-muted: #8b949e;
        --color-border: #2e2e33;
        --color-accent: #e95628;
        --color-code-bg: #1f1f23;
    }
}

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

body {
    background-color: var(--color-bg);
    color: var(--color-text);
    font-family: var(--font-sans);
    line-height: 1.6;
    padding: 2.5rem 1.5rem;
    transition: background-color 0.15s, color 0.15s;
}

.container {
    max-width: 760px;
    margin: 0 auto;
}

/* Header & Footer dividers are solid, thin lines */
header {
    margin-bottom: 2.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--color-border);
}

header h1 {
    font-size: 1.25rem;
    font-weight: 700;
}

header h1 a {
    color: var(--color-text);
    text-decoration: none;
    transition: color 0.1s;
}

header h1 a:hover {
    color: var(--color-accent);
}

header a.nav-link {
    color: var(--color-text-muted);
    font-family: var(--font-mono);
    font-size: 0.9rem;
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
}

header a.nav-link:hover {
    color: var(--color-text);
    text-decoration: underline;
}

/* Intro section */
.intro {
    margin-bottom: 2.5rem;
}

.intro p {
    color: var(--color-text-muted);
    font-size: 0.95rem;
    margin-bottom: 0.75rem;
}

.stats {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--color-accent);
}

/* Controls */
.controls {
    margin-bottom: 2.5rem;
}

.search-wrapper {
    position: relative;
    margin-bottom: 1rem;
}

.search-input {
    width: 100%;
    background-color: transparent;
    border: 1px solid var(--color-border);
    border-radius: 4px;
    padding: 0.5rem 0.8rem 0.5rem 2.2rem;
    color: var(--color-text);
    font-family: var(--font-sans);
    font-size: 0.95rem;
}

.search-input:focus {
    outline: none;
    border-color: var(--color-accent);
}

.search-icon {
    position: absolute;
    left: 0.8rem;
    top: 50%;
    transform: translateY(-50%);
    fill: var(--color-text-muted);
    pointer-events: none;
}

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

/* Dashed tags style characteristic of AstroPaper */
.filter-tag {
    background: transparent;
    border: 1px dashed var(--color-border);
    border-radius: 4px;
    color: var(--color-text-muted);
    padding: 0.25rem 0.5rem;
    font-size: 0.75rem;
    cursor: pointer;
    font-family: var(--font-mono);
    transition: all 0.1s;
}

.filter-tag:hover, .filter-tag.active {
    border-style: solid;
    border-color: var(--color-accent);
    color: var(--color-accent);
}

/* Vertical List of Problems */
.problems-list {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.problem-item {
    border-bottom: 1px solid var(--color-border);
    padding-bottom: 1.25rem;
}

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

.problem-meta-line {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--color-text-muted);
    margin-bottom: 0.2rem;
}

.problem-title-line {
    display: flex;
    justify-content: space-between;
    align-items: baseline;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.problem-title-link {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--color-accent);
    text-decoration: underline;
    text-underline-offset: 4px;
    text-decoration-color: transparent;
    transition: text-decoration-color 0.1s, color 0.1s;
}

.problem-title-link:hover {
    text-decoration-color: var(--color-accent);
}

.problem-tags-inline {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--color-text-muted);
}

/* Detail Page */
.back-link {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    color: var(--color-text-muted);
    text-decoration: none;
    font-size: 0.9rem;
    margin-bottom: 1.5rem;
    font-family: var(--font-mono);
}

.back-link:hover {
    color: var(--color-text);
}

.back-link svg {
    fill: var(--color-text-muted);
}

.back-link:hover svg {
    fill: var(--color-text);
}

.detail-title {
    font-size: 1.75rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}

.detail-meta {
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--color-text-muted);
    margin-bottom: 2rem;
}

.detail-meta a {
    color: var(--color-accent);
    text-decoration: underline;
}

.detail-meta a:hover {
    color: var(--color-text);
}

/* I/O Section */
.io-section {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1.25rem;
    margin-bottom: 2rem;
}

.io-box h3 {
    font-size: 0.8rem;
    color: var(--color-text-muted);
    margin-bottom: 0.35rem;
    font-family: var(--font-mono);
    text-transform: lowercase;
}

.io-box pre {
    background-color: var(--color-code-bg);
    border: 1px solid var(--color-border);
    border-radius: 4px;
    padding: 0.75rem;
    font-family: var(--font-mono);
    font-size: 0.85rem;
    overflow-x: auto;
    white-space: pre-wrap;
}

/* Code block wrapper matching clean papers */
.code-wrapper {
    border: 1px solid var(--color-border);
    border-radius: 4px;
    background-color: var(--color-code-bg);
    margin-top: 2rem;
    overflow: hidden;
}

.code-header {
    border-bottom: 1px solid var(--color-border);
    padding: 0.5rem 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-color: var(--color-bg);
}

.code-filename {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    color: var(--color-text-muted);
}

.code-buttons {
    display: flex;
    gap: 0.5rem;
}

.code-btn {
    background: transparent;
    border: 1px solid var(--color-border);
    border-radius: 3px;
    color: var(--color-text);
    padding: 0.2rem 0.5rem;
    font-size: 0.7rem;
    cursor: pointer;
    font-family: var(--font-mono);
    transition: border-color 0.1s;
}

.code-btn:hover {
    border-color: var(--color-accent);
    color: var(--color-accent);
}

.code-content pre {
    padding: 1.25rem;
    overflow-x: auto;
    font-family: var(--font-mono);
    font-size: 0.85rem;
    line-height: 1.5;
}

.hidden {
    display: none !important;
}

/* Minimalist Syntax Highlighting */
.j-keyword { color: #cf222e; font-weight: bold; }
.j-type { color: #953800; }
.j-string { color: #0a3069; }
.j-comment { color: #6e7781; font-style: italic; }
.j-number { color: #0550ae; }

@media (prefers-color-scheme: dark) {
    .j-keyword { color: #ff7b72; font-weight: bold; }
    .j-type { color: #ff9b50; }
    .j-string { color: #a5d6ff; }
    .j-comment { color: #8b949e; font-style: italic; }
    .j-number { color: #79c0ff; }
}