:root {
    /* colors */
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --text: #1e293b;
    --text-light: #64748b;
    --background: #ffffff;
    --background-dark: #0f172a;
    --background-light: #f1f5f9;
    --background-hover: #e2e8f0;
    --border: #e2e8f0;
    --success-bg: #dcfce7;
    --success-text: #166534;
    --text-white: #ffffff;
    --text-muted: #94a3b8;
    --text-subtitle: #cbd5e1;
    --link-color: #5492ef;
    --link-hover: #1d4ed8;
    --modal-overlay: rgba(30, 41, 59, 0.55);
    
    /* spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 2.5rem;
    
    /* border radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 1rem;
    --radius-full: 999px;
    
    /* font sizes */
    --text-xs: 0.75rem;
    --text-sm: 0.875rem;
    --text-base: 1rem;
    --text-lg: 1.1rem;
    --text-xl: 1.5rem;
    --text-2xl: 2rem;
    
    /* shadows */
    --shadow-sm: 0 2px 4px rgba(30,41,59,0.08);
    --shadow-md: 0 2px 12px rgba(30,41,59,0.08);
    --shadow-lg: 0 8px 32px rgba(30,41,59,0.18);
    
    /* container */
    --container-width: 1200px;
    --small-container-width: 600px;
}

/* base styles */

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
    background: var(--background-dark);
    color: var(--text);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
    padding: 0;
    max-width: 100vw;
    margin: 0;
}

/* layout */

.page-bg {
    min-height: 100vh;
    background: var(--background-dark);
    padding: var(--spacing-2xl) 0 4rem 0;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

.main-navbar .container,
.nav-flex,
.page-bg,
.feed-card,
.main-header {
    padding-left: 1.5rem;
    padding-right: 1.5rem;
}

@media (max-width: 640px) {
    .main-navbar .container,
    .nav-flex,
    .page-bg,
    .feed-card,
    .main-header {
        padding-left: 0.7rem;
        padding-right: 0.7rem;
    }
} 

/* header */

.navbar {
    margin-bottom: 20px;
}

.main-header {
    background: transparent;
    color: var(--text-white);
    padding: var(--spacing-xl) var(--spacing-xl) var(--spacing-lg) var(--spacing-xl);
    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
    margin-bottom: var(--spacing-2xl);
    max-width: var(--small-container-width);
    margin-left: auto;
    margin-right: auto;
    box-shadow: none;
}

.main-header-title {
    font-size: var(--text-2xl);
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.main-header-subtitle {
    font-size: var(--text-base);
    color: var(--text-subtitle);
    margin-top: var(--spacing-sm);
}

.main-header-subtitle a {
    color: var(--link-color);
    text-decoration: none;
}

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

/* cards */

.feed-card {
    background: var(--background);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border);
    padding: var(--spacing-xl) var(--spacing-2xl);
    margin-bottom: var(--spacing-xl);
    max-width: var(--container-width);
    margin-left: auto;
    margin-right: auto;
    margin-top: -1.2rem;
    position: relative;
    z-index: 2;
}

/* paper components */

.paper {
    padding: 1.2rem 0 1.2rem 0;
    border-bottom: 1px solid var(--border);
}

.paper:first-child {
    padding-top: 0;
}

.paper:last-child {
    border-bottom: none;
    padding-bottom: 0;
}

.paper h2 {
    font-size: var(--text-lg);
    font-weight: 700;
    margin-bottom: 0.4rem;
    line-height: 1.4;
}

.paper h2 a {
    color: var(--primary);
    text-decoration: none;
}

.paper h2 a:hover {
    color: var(--primary-hover);
    text-decoration: underline;
}

.paper .authors {
    margin: 0.2rem 0 0.5rem 0;
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
}

.paper .authors a {
    background: var(--background-light);
    color: var(--text-light);
    border-radius: var(--radius-full);
    padding: 0.15em 0.9em;
    font-size: var(--text-xs);
    text-decoration: none;
    font-weight: 500;
    transition: background 0.2s;
}

.paper .authors a:hover {
    background: var(--background-hover);
}

.paper .date {
    color: var(--text-light);
    font-size: 0.93rem;
    margin-bottom: 0.5rem;
}

.paper .abstract {
    color: var(--text);
    font-size: 0.97rem;
    margin-bottom: 0.5rem;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

/* recent papers section */

.recent-papers {
    border-top: none !important;
    margin-left: auto;
    margin-right: auto;
    margin-top: var(--spacing-2xl);
    margin-bottom: 0;
    padding-top: var(--spacing-lg);
    font-size: 0.95rem !important;
    color: var(--text-light);
    padding-left: var(--spacing-xl);
    padding-right: var(--spacing-xl);
    max-width: var(--small-container-width);
}

.recent-papers h3 {
    font-size: var(--text-base);
    font-weight: 500;
    margin-bottom: var(--spacing-sm);
}

.recent-papers p {
    font-size: 0.95rem;
    margin-bottom: 0.25rem;
}

.recent-papers p a {
    color: var(--text-light);
    text-decoration: none;
}

.recent-papers p a:hover {
    color: var(--link-hover);
    text-decoration: underline;
}

/* footer */

.footer-menu {
    width: 100%;
    max-width: var(--container-width);
    margin-left: auto;
    margin-right: auto;
    margin-top: var(--spacing-2xl);
    margin-bottom: 0;
    color: var(--text-light);
    font-size: 0.95rem !important;
    background: transparent;
    box-sizing: border-box;
    padding: 1.1rem var(--spacing-xl) 1.5rem var(--spacing-xl);
    display: flex;
    justify-content: center;
    align-items: center;
}

.footer-content {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
}

.footer-sep {
    color: var(--text-light);
    font-size: 1.1em;
}

.footer-menu .api-keys-link {
    background: none;
    border: none;
    color: var(--link-color);
    cursor: pointer;
    font-size: 0.95rem;
    text-decoration: none;
    padding: 0;
    margin: 0;
    font-family: inherit;
}

.footer-menu .api-keys-link:hover {
    color: var(--link-hover);
    text-decoration: underline;
}

.footer-attribution {
    color: var(--text-light);
    font-size: 0.95rem;
}

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

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

/* modal */

.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: var(--modal-overlay);
    z-index: 1000;
}

.modal {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background: var(--background);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    z-index: 1001;
    min-width: 260px;
    max-width: 95vw;
    width: 340px;
    padding: var(--spacing-xl) var(--spacing-lg) var(--spacing-lg) var(--spacing-lg);
    box-sizing: border-box;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
    align-items: stretch;
}

.modal-close {
    position: absolute;
    top: var(--spacing-md);
    right: 1.2rem;
    background: none;
    border: none;
    font-size: var(--text-2xl);
    color: var(--text-light);
    cursor: pointer;
    z-index: 1002;
    line-height: 1;
    padding: 0;
    transition: color 0.2s;
}

.modal-close:hover {
    color: var(--primary);
}

/* forms */

.form-group {
    margin-bottom: var(--spacing-lg);
}

.form-group label {
    display: block;
    font-size: var(--text-sm);
    margin-bottom: var(--spacing-sm);
    color: var(--text);
    font-weight: 500;
}

.form-group input {
    width: 100%;
    padding: var(--spacing-md);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    font-size: var(--text-sm);
    font-family: inherit;
    transition: border-color 0.2s;
}

.form-group input:focus {
    outline: none;
    border-color: var(--primary);
}

.help-text {
    font-size: var(--text-sm);
    color: var(--primary);
    margin-top: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
    background: var(--background-light);
    padding: 0.3em 0.7em;
    border-radius: var(--radius-md);
    display: block;
}

.help-text a {
    color: var(--primary-hover);
    text-decoration: underline;
    font-weight: 500;
}

/* buttons */

button[type="submit"] {
    background: var(--primary);
    color: var(--text-white);
    border: none;
    padding: var(--spacing-md);
    font-size: var(--text-sm);
    font-weight: 500;
    cursor: pointer;
    width: 100%;
    border-radius: var(--radius-md);
    transition: background-color 0.2s;
}

button[type="submit"]:hover {
    background: var(--primary-hover);
}

/* links */

.back-link {
    display: inline-flex;
    align-items: center;
    color: var(--text-light);
    text-decoration: none;
    font-size: var(--text-sm);
    margin-top: var(--spacing-lg);
    transition: color 0.2s;
}

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

/* responsive */

@media (max-width: 640px) {
    .main-header, .feed-card {
        padding: var(--spacing-lg);
        margin-left: var(--spacing-md);
        margin-right: var(--spacing-md);
    }
    
    .main-header {
        border-radius: 0;
    }
    
    .feed-card {
        border-radius: var(--radius-md);
    }
    
    .main-header-title .icon {
        display: none;
    }

    .recent-papers, .footer-menu, .footer-attribution {
        padding-left: var(--spacing-md);
        padding-right: var(--spacing-md);
    }
    
    .footer-content {
        flex-direction: column;
        gap: 0.2rem;
        text-align: center;
        width: 100%;
    }
    
    .footer-sep {
        display: none;
    }
    
    .footer-content > * {
        text-align: center;
        width: 100%;
    }
    
    .modal {
        width: 95vw;
        min-width: 0;
        padding: 1.2rem 0.7rem 1rem 0.7rem;
        max-width: 95vw;
        box-sizing: border-box;
    }
} 

/* flash messages */

.custom-flash-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    margin: 1rem auto 0rem auto;
    max-width: 400px;
}

.custom-flash {
    background: var(--success-bg);
    color: var(--success-text);
    padding: var(--spacing-md) var(--spacing-xl);
    border-radius: var(--radius-md);
    font-size: var(--text-base);
    margin-bottom: var(--spacing-sm);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--success-bg);
    width: 100%;
    text-align: center;
}

@media (max-width: 640px) {
    .custom-flash {
        min-width: 0;
        max-width: 95vw;
        padding-left: var(--spacing-md);
        padding-right: var(--spacing-md);
    }
} 

/* navbar */

.main-navbar {
    width: 100%;
    background: var(--background);
    border-bottom: 1px solid var(--border);
    padding: 0.7rem 0;
    margin-bottom: 0;
    box-shadow: 0 2px 8px rgba(30,41,59,0.03);
    position: relative;
    z-index: 10;
}

.nav-flex {
    max-width: var(--container-width);
    margin: 0 auto;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-brand-group {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
}

.navbar-brand {
    display: block;
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text);
    text-decoration: none;
    letter-spacing: -0.5px;
}

.navbar-subtitle {
    font-size: 0.98rem;
    color: var(--text-light);
    margin-left: 0;
    margin-top: 0.1em;
    font-weight: 400;
    letter-spacing: 0.01em;
}

.navbar-links {
    display: flex;
    align-items: center;
    gap: 1.2rem;
}

.navbar-links a {
    color: var(--text-light);
    text-decoration: none;
    font-size: 1rem;
    font-weight: 500;
    transition: color 0.2s;
}

.navbar-links a:hover {
    color: var(--primary);
}

@media (max-width: 640px) {
    .nav-flex {
        flex-direction: column;
        align-items: flex-start;
        padding-left: var(--spacing-md);
        padding-right: var(--spacing-md);
        gap: 0.3rem;
    }
    .navbar-links {
        gap: 0.7rem;
        margin-top: 0.2rem;
    }
    .navbar-brand {
        font-size: 1.1rem;
    }
    .navbar-subtitle {
        font-size: 0.93rem;
    }
}