/* =========================================
   1. Global Settings
   ========================================= */
:root {
    --bg-color: #0f0f12;       /* 배경: 딥 다크 */
    --card-bg: #16161a;        /* 카드 배경 */
    --accent-color: #38b6ff;   /* 포인트: 스카이 블루 */
    --text-main: #e0e0e0;
    --text-sub: #9ca3af;
    --border-color: #2a2a2a;
}

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

body {
    font-family: 'Pretendard', -apple-system, system-ui, Roboto, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.7;
    overflow-x: hidden;
}

a { text-decoration: none; color: inherit; transition: 0.3s; }
ul { list-style: none; }

/* =========================================
   2. Header & Navigation
   ========================================= */
header {
    position: fixed; width: 100%; top: 0;
    background-color: rgba(15, 15, 18, 0.9);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    display: flex; justify-content: space-between; align-items: center;
    padding: 1.2rem 5%;
}

.logo { font-size: 1.2rem; font-weight: 700; color: #fff; }
.logo span { color: var(--accent-color); font-weight: 400; }

nav ul { display: flex; gap: 2rem; font-size: 0.9rem; font-weight: 500; }
nav a:hover { color: var(--accent-color); }

.blog-link { 
    border: 1px solid var(--border-color); 
    padding: 0.3rem 0.8rem; border-radius: 4px; 
    font-size: 0.85rem; color: var(--text-sub);
}
.blog-link:hover { border-color: var(--accent-color); color: var(--accent-color); }

/* =========================================
   3. Sections Common
   ========================================= */
section { padding: 6rem 5%; max-width: 1000px; margin: 0 auto; }

h2 {
    font-size: 1.8rem; margin-bottom: 2.5rem; color: #fff;
    display: flex; align-items: center;
}
h2::before {
    content: ''; display: block; width: 4px; height: 24px;
    background: var(--accent-color); margin-right: 12px; border-radius: 2px;
}

/* =========================================
   4. Hero Section
   ========================================= */
.hero {
    height: 100vh; display: flex; flex-direction: column; justify-content: center;
    background: radial-gradient(circle at 80% 20%, #1a1a2e 0%, #0f0f12 60%);
    padding: 0 5%;
}
.hero-tag {
    color: var(--accent-color); font-weight: 600; font-size: 0.9rem;
    letter-spacing: 1px; margin-bottom: 1rem; text-transform: uppercase;
}
.hero h1 {
    font-size: 3.5rem; font-weight: 800; line-height: 1.2;
    margin-bottom: 1.5rem; color: #fff;
}
.hero h1 span { color: var(--accent-color); }
.hero p {
    font-size: 1.1rem; color: var(--text-sub);
    max-width: 650px; margin-bottom: 2.5rem;
}
.hero-btns { margin-top: 2rem; }

.btn {
    display: inline-block; padding: 0.8rem 2rem;
    background: transparent; color: #fff; font-weight: 500;
    border: 1px solid var(--border-color); border-radius: 4px;
    font-size: 0.95rem; margin-right: 10px; margin-bottom: 10px;
}
.btn:hover { border-color: var(--accent-color); color: var(--accent-color); }

/* =========================================
   5. About Grid & Profile Image
   ========================================= */
.about-grid {
    display: grid; grid-template-columns: 1fr 2fr;
    gap: 3rem; align-items: start;
}

/* 프로필 이미지 래퍼 */
.profile-img-wrapper {
    width: 100%; max-width: 300px; margin: 0 auto;
    position: relative; aspect-ratio: 1/1; /* 정사각형 비율 */
}
/* 실제 이미지 스타일 */
.avatar {
    width: 100%; height: 100%; object-fit: cover; /* 찌그러짐 방지 */
    border-radius: 12px; border: 1px solid var(--border-color);
    box-shadow: 0 4px 20px rgba(0,0,0,0.3);
}

.about-text p { margin-bottom: 1rem; color: var(--text-sub); font-size: 1rem; }
.highlight { color: #fff; font-weight: 600; }

/* 학력 박스 */
.education-box {
    margin-top: 2rem; background: rgba(255,255,255,0.03);
    padding: 1.5rem; border-radius: 8px; border: 1px solid transparent;
}
.education-box h3 {
    font-size: 1.1rem; color: #fff; margin-bottom: 1rem;
    border-bottom: 1px solid #333; padding-bottom: 0.5rem;
    display: flex; align-items: center;
}
.education-box h3::before { content: '🎓'; margin-right: 8px; font-size: 1rem; }
.education-box ul li { display: flex; flex-direction: column; gap: 0.5rem; margin-bottom: 1rem; }

.edu-header { display: flex; justify-content: space-between; align-items: center; }
.edu-year { color: var(--accent-color); font-size: 0.9rem; font-weight: 600; }
.edu-detail { font-size: 0.95rem; color: #9ca3af; }
.edu-desc { margin-bottom: 0.2rem; }
.highlight-gpa { color: var(--accent-color); margin-top: 0.3rem; font-weight: 500; }

/* =========================================
   6. Skills Cards
   ========================================= */
.card-grid {
    display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 1rem;
}
.card {
    background: var(--card-bg); padding: 2rem;
    border-radius: 8px; border: 1px solid var(--border-color); transition: 0.3s;
}
.card:hover { border-color: var(--accent-color); transform: translateY(-3px); }
.card h3 { font-size: 1.1rem; margin-bottom: 0.8rem; color: #fff; }
.card p { font-size: 0.9rem; color: var(--text-sub); margin-bottom: 1rem; }
.skill-tag {
    display: inline-block; font-size: 0.75rem; padding: 0.2rem 0.5rem;
    background: #25252b; border-radius: 4px;
    margin-right: 0.3rem; margin-bottom: 0.3rem; color: #ccc;
}

/* =========================================
   7. Research Section
   ========================================= */
.research-category { margin-bottom: 3rem; }
.research-category h3 {
    color: #fff; font-size: 1.2rem; border-bottom: 1px solid var(--border-color);
    padding-bottom: 0.8rem; margin-bottom: 1.2rem; display: flex; align-items: center; gap: 10px;
}
.research-category h3 span { font-size: 0.9rem; color: #777; font-weight: 400; }

.pub-item {
    background: rgba(255, 255, 255, 0.03); padding: 1.2rem;
    border-radius: 6px; margin-bottom: 0.8rem;
    border: 1px solid transparent; display: flex; justify-content: space-between; align-items: center;
}
.pub-item:hover { border-color: var(--border-color); }
.pub-info { flex: 1; padding-right: 1rem; }
.pub-info h4 { color: #dcdcdc; font-size: 1rem; margin-bottom: 0.4rem; font-weight: 500; }
.pub-info span { font-size: 0.85rem; color: #777; display: flex; align-items: center; flex-wrap: wrap; gap: 8px; line-height: 1.5; }

.badge-row { margin-bottom: 0.4rem; }
.cat-badge { font-size: 0.7rem; padding: 2px 8px; border-radius: 4px; font-weight: 600; margin-right: 5px; }
.badge-sky { color: #38b6ff; border: 1px solid #38b6ff; background: rgba(56,182,255,0.1); }
.badge-gray { color: #777; border: 1px solid #777; background: rgba(119,119,119,0.1); }
.badge-yellow { color: #f1c40f; border: 1px solid #f1c40f; background: rgba(241,196,15,0.1); }
.badge-red { color: #e74c3c; border: 1px solid #e74c3c; background: rgba(231,76,60,0.1); }

.status-badge {
    font-size: 0.75rem; padding: 0.2rem 0.6rem;
    border-radius: 4px; background: #25252b; color: #aaa; white-space: nowrap;
}

.pdf-btn {
    display: inline-block; font-size: 0.75rem;
    color: var(--accent-color); border: 1px solid var(--accent-color);
    padding: 2px 8px; border-radius: 4px; transition: 0.3s; margin-left: 8px;
}
.pdf-btn:hover { background: var(--accent-color); color: #fff; }

/* =========================================
   8. Projects List
   ========================================= */
.project-item {
    border-left: 2px solid var(--border-color);
    padding-left: 1.5rem; padding-bottom: 2.5rem; position: relative;
}
.project-item::before {
    content: ''; position: absolute; left: -5px; top: 5px;
    width: 8px; height: 8px; background: var(--border-color); border-radius: 50%;
}
.project-item:hover::before { background: var(--accent-color); }
.project-date { font-size: 0.85rem; color: var(--text-sub); margin-bottom: 0.3rem; display: block; }
.project-title { font-size: 1.2rem; font-weight: 700; color: #fff; margin-bottom: 0.5rem; }
.project-desc { font-size: 0.95rem; color: var(--text-sub); margin-bottom: 0.8rem; }
.project-link { font-size: 0.85rem; color: var(--accent-color); font-weight: 500; }
.project-link:hover { text-decoration: underline; }

/* =========================================
   9. Contact & Footer
   ========================================= */
.contact-box {
    text-align: left; padding: 3rem; background: var(--card-bg);
    border-radius: 8px; border: 1px solid var(--border-color);
    display: flex; justify-content: space-between; align-items: center;
}
.contact-info div { font-size: 1.1rem; font-weight: 600; color: #fff; }
.contact-info span { font-size: 0.9rem; color: var(--text-sub); display: block; margin-top: 0.5rem; }

footer {
    background-color: var(--card-bg); border-top: 1px solid var(--border-color);
    padding: 3rem 0; text-align: center; margin-top: 6rem;
}
.footer-content p { color: var(--text-main); font-size: 0.95rem; margin-bottom: 0.3rem; }
.footer-sub { color: var(--text-sub) !important; font-size: 0.8rem !important; }

/* =========================================
   10. Mobile Responsiveness
   ========================================= */
@media (max-width: 768px) {
    .hero h1 { font-size: 2.5rem; }
    .about-grid { grid-template-columns: 1fr; }
    nav ul { display: none; }
    .pub-item { flex-direction: column; align-items: flex-start; gap: 0.8rem; }
    .status-badge { align-self: flex-start; margin-top: 5px; }
    .contact-box { flex-direction: column; text-align: center; gap: 1.5rem; }
    .btn { width: 100%; margin-right: 0; }
}