/* GTAIScience - Layout System */

.container {
    width: 100%;
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 var(--content-padding);
}

.container-fluid {
    width: 100%;
    padding: 0 var(--content-padding);
}

/* App Layout */
#app {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.main-content {
    flex: 1;
    padding-top: var(--header-height);
}

/* Header */
.site-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: var(--color-bg-overlay);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--color-border);
    z-index: var(--z-fixed);
    transition: background var(--transition-base);
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 var(--content-padding);
}

.header-logo {
    display: flex;
    align-items: center;
    gap: var(--space-3);
    font-size: var(--font-size-xl);
    font-weight: var(--font-weight-bold);
    color: var(--color-text-primary);
}

.header-logo img {
    height: 36px;
    width: auto;
}

.header-nav {
    display: flex;
    align-items: center;
    gap: var(--space-8);
}

.nav-link {
    position: relative;
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    padding: var(--space-2) 0;
    transition: color var(--transition-base);
}

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

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--gradient-primary);
    border-radius: var(--radius-full);
}

.header-actions {
    display: flex;
    align-items: center;
    gap: var(--space-4);
}

/* Mobile menu toggle */
.menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    padding: var(--space-2);
    cursor: pointer;
}

.menu-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-text-primary);
    transition: var(--transition-base);
}

/* Footer */
.site-footer {
    background: var(--color-bg-secondary);
    border-top: 1px solid var(--color-border);
    padding: var(--space-16) 0 var(--space-8);
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: var(--space-12);
    margin-bottom: var(--space-12);
}

.footer-brand {
    max-width: 320px;
}

.footer-brand p {
    margin-top: var(--space-4);
    font-size: var(--font-size-sm);
}

.footer-col h4 {
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-semibold);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--color-text-primary);
    margin-bottom: var(--space-4);
}

.footer-col ul li {
    margin-bottom: var(--space-2);
}

.footer-col ul li a {
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
    transition: color var(--transition-fast);
}

.footer-col ul li a:hover {
    color: var(--color-primary-light);
}

.footer-bottom {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: var(--space-8);
    border-top: 1px solid var(--color-border);
    font-size: var(--font-size-sm);
    color: var(--color-text-muted);
}

/* Grid System */
.grid {
    display: grid;
    gap: var(--space-6);
}

.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }

/* Flexbox utilities */
.flex { display: flex; }
.flex-col { flex-direction: column; }
.flex-center { align-items: center; justify-content: center; }
.flex-between { justify-content: space-between; }
.flex-wrap { flex-wrap: wrap; }
.gap-2 { gap: var(--space-2); }
.gap-4 { gap: var(--space-4); }
.gap-6 { gap: var(--space-6); }
.gap-8 { gap: var(--space-8); }

/* Section spacing */
.section {
    padding: var(--space-20) 0;
}

.section-header {
    text-align: center;
    margin-bottom: var(--space-12);
}

.section-header h2 {
    margin-bottom: var(--space-4);
}

.section-header p {
    max-width: 600px;
    margin: 0 auto;
    font-size: var(--font-size-lg);
}