/* ============================================
   SHARED STYLES — Koyilbek Valiev Portfolio
   Used by: index.html, research.html, projects.html
   ============================================ */

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

:root {
    --bg: #ffffff;
    --bg-alt: #f8fafc;
    --text: #1a1a2e;
    --text-secondary: #4a5568;
    --text-muted: #718096;
    --accent: #2563EB;
    --accent-hover: #1d4ed8;
    --accent-light: #eff6ff;
    --border: #e5e7eb;
    --border-light: #f3f4f6;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07);
    --radius: 8px;
    --max-width: 800px;
    --transition: 0.2s ease;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: 72px;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.7;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

::selection {
    background: var(--accent);
    color: #fff;
}

/* ============================================
   NAVIGATION
   ============================================ */
.nav {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.92);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
}

.nav-inner {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1.5rem;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-name {
    font-weight: 700;
    font-size: 1rem;
    color: var(--text);
    text-decoration: none;
}

.nav-links {
    display: flex;
    list-style: none;
    gap: 0.25rem;
}

.nav-links a {
    color: var(--text-muted);
    text-decoration: none;
    font-size: 0.85rem;
    font-weight: 500;
    padding: 0.35rem 0.65rem;
    border-radius: 6px;
    transition: var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--accent);
    background: var(--accent-light);
}

.nav-hamburger {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
    flex-direction: column;
    gap: 4px;
}

.nav-hamburger span {
    width: 20px;
    height: 2px;
    background: var(--text);
    border-radius: 1px;
    transition: var(--transition);
}

/* ============================================
   LAYOUT
   ============================================ */
.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 1.5rem;
}

.section {
    padding: 3.5rem 0;
    border-bottom: 1px solid var(--border-light);
}

.section:last-of-type {
    border-bottom: none;
}

.section-alt {
    background: var(--bg-alt);
}

.section-title {
    font-size: 1.35rem;
    font-weight: 700;
    color: var(--text);
    margin-bottom: 1.75rem;
    letter-spacing: -0.02em;
}

.section-title i {
    color: var(--accent);
    margin-right: 0.5rem;
    font-size: 1.1rem;
}

/* ============================================
   PAGE HEADER (for sub-pages)
   ============================================ */
.page-header {
    padding: 3rem 0 2rem;
    border-bottom: 1px solid var(--border-light);
}

.page-header h1 {
    font-size: 2rem;
    font-weight: 800;
    letter-spacing: -0.03em;
    margin-bottom: 0.5rem;
}

.page-header p {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

/* ============================================
   BUTTONS
   ============================================ */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    padding: 0.5rem 1.25rem;
    font-size: 0.85rem;
    font-weight: 600;
    border-radius: 6px;
    text-decoration: none;
    transition: var(--transition);
    border: none;
    cursor: pointer;
    font-family: inherit;
}

.btn-primary {
    background: var(--accent);
    color: #fff;
}

.btn-primary:hover {
    background: var(--accent-hover);
}

.btn-outline {
    background: var(--bg);
    color: var(--text);
    border: 1px solid var(--border);
}

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

/* ============================================
   FOOTER
   ============================================ */
.footer {
    border-top: 1px solid var(--border);
    padding: 2rem 0;
    text-align: center;
}

.footer p {
    font-size: 0.8rem;
    color: var(--text-muted);
}

/* ============================================
   RESPONSIVE
   ============================================ */
@media (max-width: 768px) {
    .nav-links {
        display: none;
        position: absolute;
        top: 56px;
        left: 0;
        right: 0;
        background: rgba(255, 255, 255, 0.98);
        backdrop-filter: blur(12px);
        -webkit-backdrop-filter: blur(12px);
        border-bottom: 1px solid var(--border);
        flex-direction: column;
        padding: 0.75rem 1.5rem;
    }

    .nav-links.open {
        display: flex;
    }

    .nav-hamburger {
        display: flex;
    }

    .section {
        padding: 2.5rem 0;
    }

    .page-header h1 {
        font-size: 1.5rem;
    }
}