/* Theme Variables */
:root {
    /* Color Palette - Stanford/arXiv inspired */
    --primary: #8C1515;           /* Stanford Red */
    --primary-dark: #6a1010;
    --secondary: #003366;         /* arXiv Blue */
    --accent: #b31b1b;            /* Cornell Red/Accent */
    --bg-main: #ffffff;
    --bg-subtle: #f8f9fa;
    --bg-arxiv: #f4f4f4;
    --border: #dddddd;
    --text-main: #2e2e2e;
    --text-muted: #5e5e5e;
    --link-color: #004b91;

    /* Typography */
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    --font-serif: "Georgia", "Times New Roman", serif;
}

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

body {
    font-family: var(--font-sans);
    background: var(--bg-main);
    color: var(--text-main);
    line-height: 1.6;
}

a {
    color: var(--link-color);
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

/* Header & Navigation */
header {
    background: white;
    border-top: 3px solid var(--primary);
    border-bottom: 1px solid var(--border);
    padding: 1rem 2rem;
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1100px;
    margin: 0 auto;
}

.brand {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary);
    text-transform: uppercase;
    letter-spacing: -0.5px;
    text-decoration: none;
}

.brand:hover {
    text-decoration: none;
}

.nav-links {
    display: flex;
    gap: 1.5rem;
    font-size: 0.9rem;
}

.nav-links a {
    color: var(--text-muted);
}

.nav-links a:hover {
    color: var(--primary);
    text-decoration: none;
}

/* Home page */
.home-container {
    max-width: 900px;
    margin: 0 auto;
    padding: 60px 20px;
}

.hero {
    text-align: center;
    margin-bottom: 3rem;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
    color: var(--text-main);
}

.tagline {
    font-size: 1.2rem;
    color: var(--text-muted);
    font-family: var(--font-serif);
}

.how-to {
    background: var(--bg-arxiv);
    border-radius: 4px;
    padding: 1.5rem;
    margin-bottom: 2rem;
    border-left: 5px solid var(--secondary);
}

.how-to h2 {
    font-size: 1.1rem;
    margin-bottom: 0.75rem;
    color: var(--secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.url-transform {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    flex-wrap: wrap;
    margin-top: 1rem;
}

.url {
    font-family: monospace;
    font-size: 0.9rem;
    padding: 0.5rem 1rem;
    border-radius: 4px;
}

.url.old {
    background: #e9ecef;
    color: var(--text-muted);
}

.url.new {
    background: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
}

.url strong {
    font-weight: bold;
}

.arrow {
    font-size: 1.5rem;
    color: var(--primary);
}

.try-it {
    background: white;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 2rem;
    margin-bottom: 2rem;
    text-align: center;
}

.try-it h2 {
    font-size: 1.1rem;
    margin-bottom: 1rem;
    color: var(--text-main);
}

#paper-form {
    display: flex;
    gap: 0.5rem;
    max-width: 550px;
    margin: 0 auto;
}

#paper-input {
    flex: 1;
    padding: 0.75rem 1rem;
    font-size: 1rem;
    border: 1px solid var(--border);
    border-radius: 4px;
    outline: none;
    transition: border-color 0.2s, box-shadow 0.2s;
}

#paper-input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 2px rgba(140, 21, 21, 0.1);
}

#paper-form button {
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-weight: 600;
    transition: background 0.2s;
}

#paper-form button:hover {
    background: var(--primary-dark);
}

/* Feature Cards */
.features {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: 1.5rem;
    margin-top: 3rem;
}

.feature {
    background: white;
    padding: 1.5rem;
    border: 1px solid var(--border);
    border-radius: 8px;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.feature:hover {
    transform: translateY(-4px);
    box-shadow: 0 10px 20px rgba(0,0,0,0.05);
}

.feature h3 {
    font-size: 1rem;
    margin-bottom: 0.5rem;
    color: var(--primary);
    font-weight: 700;
}

.feature p {
    font-size: 0.9rem;
    color: var(--text-muted);
    font-family: var(--font-serif);
}

/* Chat page */
.chat-container {
    display: flex;
    flex-direction: column;
    height: 100vh;
    max-width: 900px;
    margin: 0 auto;
    background: white;
    box-shadow: 0 0 20px rgba(0, 0, 0, 0.08);
}

.chat-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 1.5rem;
    border-top: 3px solid var(--primary);
    border-bottom: 1px solid var(--border);
    background: white;
}

.header-left .logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary);
    text-transform: uppercase;
    letter-spacing: -0.5px;
    text-decoration: none;
}

.header-left .logo:hover {
    text-decoration: none;
}

.header-center {
    flex: 1;
    text-align: center;
    padding: 0 1rem;
}

.paper-link {
    font-size: 0.9rem;
    color: var(--text-muted);
    font-family: var(--font-serif);
}

.paper-link:hover {
    color: var(--secondary);
    text-decoration: none;
}

.header-right {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.share-btn {
    padding: 0.5rem 1rem;
    font-size: 0.85rem;
    background: var(--secondary);
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-weight: 600;
    transition: background 0.2s;
}

.share-btn:hover {
    background: #002244;
}

/* Status banner */
.status-banner {
    padding: 0.75rem 1.5rem;
    background: #fff3cd;
    border-bottom: 1px solid #ffc107;
}

#status-text {
    display: block;
    font-size: 0.85rem;
    color: #856404;
    margin-bottom: 0.5rem;
}

.progress-bar {
    height: 4px;
    background: #e9ecef;
    border-radius: 2px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: #ffc107;
    transition: width 0.3s ease;
}

/* Messages area */
.chat-messages {
    flex: 1;
    overflow-y: auto;
    padding: 1.5rem;
    background: var(--bg-subtle);
}

.welcome-message {
    text-align: center;
    padding: 3rem 1rem;
    color: var(--text-muted);
    font-family: var(--font-serif);
}

.message {
    margin-bottom: 1rem;
    max-width: 80%;
}

.message.user {
    margin-left: auto;
}

.message.assistant {
    margin-right: auto;
}

.message-content {
    padding: 0.75rem 1rem;
    border-radius: 8px;
    white-space: pre-wrap;
    word-break: break-word;
}

.message.user .message-content {
    background: var(--primary);
    color: white;
    border-bottom-right-radius: 2px;
}

.message.assistant .message-content {
    background: white;
    color: var(--text-main);
    border: 1px solid var(--border);
    border-left: 3px solid var(--secondary);
    border-bottom-left-radius: 2px;
}

.message.loading .message-content {
    color: var(--text-muted);
}

.dots {
    animation: blink 1s infinite;
}

@keyframes blink {
    0%, 50% { opacity: 1; }
    51%, 100% { opacity: 0.3; }
}

/* Citations */
.citations {
    margin-top: 0.75rem;
    font-size: 0.85rem;
}

.citations summary {
    cursor: pointer;
    color: var(--secondary);
    padding: 0.25rem 0;
    font-weight: 600;
}

.citation {
    padding: 0.75rem;
    margin-top: 0.5rem;
    background: var(--bg-arxiv);
    border-left: 3px solid var(--secondary);
    border-radius: 0 4px 4px 0;
}

.citation .page {
    font-weight: bold;
    color: var(--secondary);
    font-size: 0.8rem;
}

.citation p {
    margin-top: 0.25rem;
    color: var(--text-muted);
    font-family: var(--font-serif);
    font-size: 0.9rem;
}

/* Chat input */
.chat-input-container {
    padding: 1rem 1.5rem;
    border-top: 1px solid var(--border);
    background: white;
}

#chat-form {
    display: flex;
    gap: 0.5rem;
}

#message-input {
    flex: 1;
    padding: 0.75rem 1rem;
    font-size: 1rem;
    font-family: inherit;
    border: 1px solid var(--border);
    border-radius: 4px;
    outline: none;
    transition: border-color 0.2s, box-shadow 0.2s;
    resize: none;
    min-height: 44px;
    max-height: 200px;
    overflow-y: auto;
}

#message-input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 2px rgba(140, 21, 21, 0.1);
}

#message-input:disabled {
    background: var(--bg-subtle);
    cursor: not-allowed;
}

#send-btn {
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-weight: 600;
    transition: background 0.2s;
}

#send-btn:hover:not(:disabled) {
    background: var(--primary-dark);
}

#send-btn:disabled {
    background: var(--border);
    cursor: not-allowed;
}

/* Responsive */
@media (max-width: 850px) {
    nav {
        flex-direction: column;
        gap: 0.75rem;
    }

    .nav-links {
        gap: 1rem;
    }
}

@media (max-width: 600px) {
    header {
        padding: 1rem;
    }

    .chat-header {
        flex-direction: column;
        gap: 0.5rem;
        padding: 1rem;
    }

    .header-center {
        order: -1;
    }

    .message {
        max-width: 90%;
    }

    .url-transform {
        flex-direction: column;
    }

    .arrow {
        transform: rotate(90deg);
    }

    .hero h1 {
        font-size: 2rem;
    }

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