:root {
    --hanyang-blue: #003666;
    --hanyang-blue-dark: #001f3d;
    --hanyang-gold: #8b7141;
    --hanyang-gold-light: #a6884e;
    --white: #ffffff;
    --gray-50: #f9f9f9;
    --gray-100: #f1f1f1;
    --gray-200: #e2e2e2;
    --gray-800: #333333;
    --text-primary: #1a1a1a;
    --text-secondary: #666666;
    --transition-fast: all 0.2s ease;
    --transition-normal: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 10px 25px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 20px 40px rgba(0, 0, 0, 0.12);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, sans-serif;
    color: var(--text-primary);
    line-height: 1.6;
    background-color: var(--white);
    overflow-x: hidden;
}

a {
    text-decoration: none;
    color: inherit;
    transition: var(--transition-fast);
}

ul {
    list-style: none;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 25px;
}

/* Header & Nav */
header {
    height: 80px;
    display: flex;
    align-items: center;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(15px);
    -webkit-backdrop-filter: blur(15px);
    z-index: 1000;
    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
    transition: var(--transition-normal);
}

header.scrolled {
    height: 65px;
    background: rgba(255, 255, 255, 0.95);
    box-shadow: var(--shadow-sm);
}

.header-inner {
    display: flex;
    justify-content: space-between;
    align-items: center;
    width: 100%;
}

.logo {
    font-size: 1.4rem;
    font-weight: 800;
    color: var(--hanyang-blue);
    display: flex;
    align-items: center;
    gap: 8px;
    letter-spacing: -0.5px;
}

.logo span {
    color: var(--hanyang-gold);
}

nav ul {
    display: flex;
    gap: 35px;
}

nav ul li a {
    font-weight: 600;
    font-size: 1rem;
    color: var(--text-primary);
    position: relative;
}

nav ul li a::after {
    content: '';
    position: absolute;
    width: 0;
    height: 2px;
    bottom: -5px;
    left: 0;
    background-color: var(--hanyang-gold);
    transition: var(--transition-normal);
}

nav ul li a:hover {
    color: var(--hanyang-blue);
}

nav ul li a:hover::after {
    width: 100%;
}

/* Hero Section */
.hero {
    height: 70vh;
    min-height: 500px;
    background: radial-gradient(circle at top right, #004a8d, var(--hanyang-blue-dark));
    display: flex;
    align-items: center;
    color: var(--white);
    padding-top: 80px;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    width: 150%;
    height: 150%;
    background: url('https://www.transparenttextures.com/patterns/cubes.png');
    opacity: 0.05;
    animation: move-bg 60s linear infinite;
}

@keyframes move-bg {
    from {
        transform: translate(0, 0);
    }

    to {
        transform: translate(-5%, -5%);
    }
}

.hero-content {
    position: relative;
    z-index: 2;
    padding-bottom: 40px;
}

.hero h1 {
    font-size: 3.5rem;
    font-weight: 800;
    margin-bottom: 20px;
    line-height: 1.1;
    letter-spacing: -1.5px;
}

.hero p {
    font-size: 1.2rem;
    font-weight: 400;
    opacity: 0.85;
    margin-bottom: 35px;
    max-width: 650px;
}

/* Scroll Down Indicator */
.scroll-indicator {
    position: absolute;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    opacity: 0.5;
    transition: var(--transition-normal);
}

.mouse {
    width: 24px;
    height: 40px;
    border: 2px solid var(--white);
    border-radius: 12px;
    position: relative;
}

.wheel {
    width: 4px;
    height: 8px;
    background: var(--white);
    border-radius: 2px;
    position: absolute;
    top: 6px;
    left: 50%;
    margin-left: -2px;
    animation: scroll-wheel 1.5s ease-out infinite;
}

@keyframes scroll-wheel {
    0% {
        transform: translateY(0);
        opacity: 1;
    }

    100% {
        transform: translateY(15px);
        opacity: 0;
    }
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 16px 36px;
    border-radius: 10px;
    font-weight: 700;
    font-size: 1.05rem;
    transition: var(--transition-normal);
    cursor: pointer;
    border: none;
}

.btn-primary {
    background-color: var(--hanyang-gold);
    color: var(--white);
    box-shadow: 0 10px 20px rgba(139, 113, 65, 0.3);
}

.btn-primary:hover {
    background-color: var(--hanyang-gold-light);
    transform: translateY(-3px);
    box-shadow: 0 15px 30px rgba(139, 113, 65, 0.4);
}

/* Sections */
section {
    padding: 120px 0;
}

.section-title {
    text-align: center;
    margin-bottom: 70px;
}

.section-title h2 {
    font-size: 2.5rem;
    color: var(--hanyang-blue);
    margin-bottom: 15px;
    font-weight: 800;
    letter-spacing: -1px;
}

.section-title p {
    font-size: 1.1rem;
    color: var(--text-secondary);
}

/* Recruitment Banner */
.recruit-banner {
    background: var(--white);
    border-radius: 16px;
    padding: 35px 45px;
    margin-top: -60px;
    position: relative;
    z-index: 10;
    box-shadow: var(--shadow-lg);
    display: flex;
    justify-content: space-between;
    align-items: center;
    border: 1px solid rgba(0, 0, 0, 0.05);
}

.recruit-banner h4 {
    color: var(--hanyang-blue);
    font-size: 1.25rem;
    margin-bottom: 8px;
    font-weight: 700;
}

.recruit-banner p {
    color: var(--text-secondary);
    font-size: 1rem;
}

/* Cards */
.grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 30px;
}

.card {
    background: var(--white);
    border-radius: 20px;
    padding: 40px;
    transition: var(--transition-normal);
    border: 1px solid var(--gray-100);
    display: flex;
    flex-direction: column;
}

.card:hover {
    transform: translateY(-10px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(0, 54, 102, 0.1);
}

.tag {
    display: inline-block;
    padding: 5px 14px;
    border-radius: 6px;
    font-size: 0.8rem;
    font-weight: 700;
    margin-bottom: 20px;
    width: fit-content;
}

.tag-blue {
    background: rgba(0, 54, 102, 0.07);
    color: var(--hanyang-blue);
}

.card h3 {
    font-size: 1.35rem;
    margin-bottom: 20px;
    color: var(--text-primary);
    font-weight: 700;
}

.card .date {
    font-size: 0.95rem;
    color: var(--text-secondary);
    margin-top: auto;
}

/* Infrastructure */
.infra-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 25px;
}

.infra-card {
    background: var(--gray-50);
    padding: 45px;
    border-radius: 20px;
    text-align: center;
    transition: var(--transition-normal);
    cursor: pointer;
    border: 1px solid transparent;
}

.infra-card:hover {
    background: var(--white);
    border-color: var(--hanyang-blue);
    box-shadow: var(--shadow-md);
    transform: scale(1.02);
}

.infra-card .icon {
    font-size: 2.8rem;
    margin-bottom: 20px;
    display: block;
}

.infra-card p {
    font-weight: 700;
    font-size: 1.15rem;
    color: var(--hanyang-blue);
}

/* Back to Top */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background: var(--hanyang-blue);
    color: var(--white);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition-normal);
    z-index: 999;
    box-shadow: var(--shadow-md);
}

.back-to-top.show {
    opacity: 1;
    visibility: visible;
}

.back-to-top:hover {
    background: var(--hanyang-gold);
    transform: translateY(-5px);
}

/* Responsive */
@media (max-width: 768px) {
    .hero h1 {
        font-size: 2.5rem;
    }

    .hero p {
        font-size: 1.1rem;
    }

    .recruit-banner {
        flex-direction: column;
        text-align: center;
        gap: 20px;
        padding: 30px;
    }

    nav {
        display: none;
    }

    /* Mobile menu hack: just hide for now */
    .section-title h2 {
        font-size: 2rem;
    }
}