/* styles.css */
:root {
    --primary-color: #2563eb; /* 딥하고 세련된 블루 */
    --secondary-color: #1e40af;
    --accent-color: #0f172a; /* 아주 짙은 네이비/슬레이트 (고급스러움) */
    --text-main: #1e293b;
    --text-light: #64748b;
    --bg-main: #ffffff;
    --bg-alt: #f8fafc; /* 깔끔하고 차가운 회백색 */
    --bg-dark: #0f172a; 
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    /* 글로벌 폰트로 Pretendard 적용 (세련됨의 상징) */
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, sans-serif;
}

body {
    color: var(--text-main);
    line-height: 1.6;
    background-color: var(--bg-main);
}

html {
    scroll-behavior: smooth;
}

h1, h2, h3, h4 {
    font-weight: 700;
    color: var(--accent-color);
    letter-spacing: -0.5px;
}

/* Navigation */
nav {
    position: fixed;
    top: 0;
    width: 100%;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(8px);
    padding: 1.2rem 5%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 1px 0 rgba(0,0,0,0.05);
    z-index: 1000;
}

.logo {
    font-size: 1.4rem;
    font-weight: 800;
    color: var(--accent-color);
    letter-spacing: -0.5px;
}

.nav-links {
    list-style: none;
    display: flex;
    gap: 2.5rem;
    align-items: center;
}

.nav-links a {
    text-decoration: none;
    color: var(--text-main);
    font-weight: 600;
    font-size: 1rem;
    transition: color 0.3s;
}

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

.login-btn {
    background-color: var(--accent-color);
    color: white !important;
    padding: 0.5rem 1.2rem;
    border-radius: 4px;
    font-size: 0.9rem !important;
}

.login-btn:hover {
    background-color: #334155;
}

/* Sections */
.section {
    padding: 7rem 10%;
}

.section-desc {
    text-align: center;
    color: var(--text-light);
    font-size: 1.1rem;
    margin-top: -1.5rem;
    margin-bottom: 3.5rem;
    font-weight: 400;
}

.bg-light { background-color: var(--bg-alt); }
.bg-dark { background-color: var(--bg-dark); color: white; }
.text-white { color: white; }

h2 {
    font-size: 2.2rem;
    margin-bottom: 2rem;
    text-align: center;
}

/* Hero Section */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    background: linear-gradient(135deg, #f8fafc 0%, #e2e8f0 100%);
    padding: 120px 20px 60px;
}

.profile-img-container {
    margin-bottom: 2rem;
}

.profile-img {
    width: 130px;
    height: 130px;
    border-radius: 50%;
    object-fit: cover;
    box-shadow: 0 10px 25px rgba(0,0,0,0.1);
    border: 3px solid white;
}

.hero h1 {
    font-size: 3.2rem;
    line-height: 1.35;
    margin-bottom: 1.5rem;
}

.highlight {
    color: var(--primary-color);
}

.hero p {
    font-size: 1.15rem;
    color: var(--text-main);
    margin-bottom: 2.5rem;
    font-weight: 400;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
}

.btn {
    display: inline-block;
    padding: 1rem 2.5rem;
    background-color: var(--primary-color);
    color: white;
    text-decoration: none;
    border-radius: 6px;
    font-size: 1.05rem;
    font-weight: 600;
    transition: all 0.3s;
    border: none;
    cursor: pointer;
}

.btn:hover {
    background-color: var(--secondary-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.2);
}

.btn-outline {
    background-color: transparent;
    color: var(--accent-color);
    border: 1px solid #cbd5e1;
}

.btn-outline:hover {
    background-color: white;
    color: var(--accent-color);
    border-color: var(--accent-color);
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
}

/* Curriculum Cards */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.card {
    background: white;
    padding: 3rem 2.5rem;
    border-radius: 8px; /* 각진 느낌으로 세련됨 강조 */
    box-shadow: 0 4px 6px rgba(0,0,0,0.02);
    text-align: left;
    transition: transform 0.3s, box-shadow 0.3s;
    border: 1px solid #e2e8f0;
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 12px 24px rgba(0,0,0,0.06);
    border-color: #cbd5e1;
}

.card-title-wrap {
    display: flex;
    flex-direction: column;
    margin-bottom: 1.5rem;
}

.step-num {
    font-size: 0.9rem;
    font-weight: 800;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
    letter-spacing: 1px;
}

.card h3 {
    font-size: 1.4rem;
    line-height: 1.4;
}

.card p {
    color: var(--text-light);
    font-size: 1rem;
}

/* Materials Board */
.materials-board {
    max-width: 900px;
    margin: 0 auto;
    background: white;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.02);
    border: 1px solid #e2e8f0;
}

.material-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 2rem;
    border-bottom: 1px solid #e2e8f0;
    transition: background-color 0.2s;
}

.material-item:last-child {
    border-bottom: none;
}

.material-item:hover {
    background-color: #f8fafc;
}

.material-info h4 {
    font-size: 1.15rem;
    margin: 0.5rem 0;
}

.material-date {
    font-size: 0.9rem;
    color: var(--text-light);
}

.badge {
    display: inline-block;
    padding: 0.25rem 0.6rem;
    border-radius: 4px;
    font-size: 0.75rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    letter-spacing: 0.5px;
}

.badge.new {
    background-color: #ef4444;
    color: white;
}

.badge.auth {
    background-color: var(--accent-color);
    color: white;
}

.download-btn {
    padding: 0.6rem 1.2rem;
    background-color: white;
    color: var(--accent-color);
    border: 1px solid #cbd5e1;
    border-radius: 4px;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.download-btn:hover {
    background-color: var(--bg-alt);
    border-color: var(--accent-color);
}

.download-btn.auth-required {
    background-color: #f1f5f9;
    color: #94a3b8;
    border-color: #e2e8f0;
    cursor: not-allowed;
}

/* QnA Board */
.qna-board {
    max-width: 900px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.qna-item {
    background: white;
    padding: 1.5rem 2rem;
    border-radius: 8px;
    border: 1px solid #e2e8f0;
    border-left: 4px solid #cbd5e1;
    transition: transform 0.2s;
}

.qna-item:hover {
    transform: translateX(5px);
}

.qna-item.answered-ai { border-left-color: #6366f1; }
.qna-item.answered-teacher { border-left-color: var(--primary-color); }
.qna-item.waiting { border-left-color: #f59e0b; }

.qna-status {
    font-size: 0.85rem;
    font-weight: 700;
    margin-bottom: 0.8rem;
    color: #f59e0b;
    letter-spacing: -0.5px;
}

.qna-status.teacher { color: var(--primary-color); }
.qna-item.answered-ai .qna-status { color: #6366f1; }

.qna-item h4 {
    font-size: 1.1rem;
    margin-bottom: 0.5rem;
}

.qna-author {
    font-size: 0.9rem;
    color: var(--text-light);
}

.qna-action {
    text-align: center;
    margin-top: 2rem;
}

/* YouTube Section */
.video-placeholder {
    width: 100%;
    aspect-ratio: 16/9;
    background-color: #1e293b;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform 0.3s;
}

.video-placeholder:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(0,0,0,0.1);
}

.play-icon {
    font-size: 3rem;
    color: white;
    opacity: 0.8;
    transition: opacity 0.2s, transform 0.2s;
}

.video-placeholder:hover .play-icon {
    opacity: 1;
    transform: scale(1.1);
    color: #ef4444; /* YouTube Red on hover */
}

/* Footer & Social Buttons */
footer {
    padding: 4rem 10% 2rem;
}

.footer-content {
    display: flex;
    justify-content: center;
    margin-bottom: 2rem;
}

.footer-info {
    text-align: center;
}

.social-btn {
    text-decoration: none;
    padding: 0.6rem 1.5rem;
    border-radius: 30px;
    font-size: 0.95rem;
    font-weight: 600;
    transition: opacity 0.2s, transform 0.2s;
}

.social-btn:hover {
    opacity: 0.9;
    transform: translateY(-2px);
}

.social-btn.kakao { background-color: #FEE500; color: #000000; }
.social-btn.insta { background-color: #E1306C; color: #ffffff; }
.social-btn.blog { background-color: #03C75A; color: #ffffff; }

.footer-bottom {
    text-align: center;
    border-top: 1px solid #1e293b;
    padding-top: 2rem;
    color: #475569;
    font-size: 0.9rem;
}

/* Responsive */
@media (max-width: 768px) {
    .nav-links { display: none; }
    .hero h1 { font-size: 2.2rem; }
    .profile-img { width: 100px; height: 100px; }
    .material-item {
        flex-direction: column;
        align-items: flex-start;
        gap: 1rem;
    }
}