@import url("https://cdn.jsdelivr.net/gh/orioncactus/pretendard@v1.3.9/dist/web/variable/pretendardvariable-dynamic-subset.min.css");

:root {
  --bg: #ffffff;
  --surface: #fafafa;
  --line: #ececec;
  --line-strong: #dcdcdc;
  --text: #111111;
  --text-sub: #555555;
  --text-mute: #8a8a8a;

  --physics: #2f6bff;
  --physics-soft: #eef3ff;
  --chemistry: #ff7a1a;
  --chemistry-soft: #fff3ea;
  --biology: #17a34a;
  --biology-soft: #ebf8f0;
  --earth: #0e9aa7;
  --earth-soft: #e8f7f8;

  --radius: 18px;
  --max: 1120px;
}

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

html { -webkit-text-size-adjust: 100%; }

body {
  font-family: "Pretendard Variable", Pretendard, -apple-system, BlinkMacSystemFont, "Apple SD Gothic Neo", "Noto Sans KR", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

a { color: inherit; text-decoration: none; }

.container { width: 100%; max-width: var(--max); margin: 0 auto; padding: 0 24px; }

/* ---------- Hero ---------- */
.hero { padding: 96px 0 72px; text-align: center; }
.eyebrow {
  display: inline-block; padding: 6px 12px; border: 1px solid var(--line-strong); border-radius: 999px;
  font-size: 13px; font-weight: 600; color: var(--text-sub); margin-bottom: 24px;
}
.hero h1 { font-size: clamp(36px, 6vw, 64px); font-weight: 800; line-height: 1.15; letter-spacing: -0.035em; }
.hero h1 .hl { background: linear-gradient(90deg, var(--physics), var(--chemistry), var(--biology), var(--earth)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.hero p { margin: 20px auto 0; max-width: 560px; font-size: 18px; color: var(--text-sub); }
.hero-actions { margin-top: 36px; display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }
.btn {
  display: inline-flex; align-items: center; gap: 8px; height: 48px; padding: 0 22px; border-radius: 999px;
  font-size: 16px; font-weight: 600; border: 1px solid var(--line-strong); background: var(--bg); transition: transform .15s, box-shadow .15s;
}
.btn:hover { transform: translateY(-1px); box-shadow: 0 6px 20px rgba(0,0,0,.06); }
.btn-primary { background: var(--text); color: #fff; border-color: var(--text); }

/* ---------- Section ---------- */
.section { padding: 48px 0 96px; }
.section-head { display: flex; align-items: end; justify-content: space-between; gap: 16px; margin-bottom: 28px; }
.section-head h2 { font-size: 28px; font-weight: 800; letter-spacing: -0.02em; }
.section-head p { color: var(--text-mute); font-size: 15px; }

/* ---------- Category cards ---------- */
.categories { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
.cat-card {
  --accent: var(--text); --soft: var(--surface);
  position: relative; display: flex; flex-direction: column; gap: 14px; min-height: 260px; padding: 32px;
  border: 1px solid var(--line); border-radius: var(--radius); background: var(--bg); overflow: hidden;
  transition: border-color .2s, transform .2s, box-shadow .2s;
}
.cat-card:hover { border-color: var(--accent); transform: translateY(-3px); box-shadow: 0 16px 40px rgba(0,0,0,.06); }
.cat-card.physics { --accent: var(--physics); --soft: var(--physics-soft); }
.cat-card.chemistry { --accent: var(--chemistry); --soft: var(--chemistry-soft); }
.cat-card.biology { --accent: var(--biology); --soft: var(--biology-soft); }
.cat-card.earth { --accent: var(--earth); --soft: var(--earth-soft); }
.cat-icon {
  width: 56px; height: 56px; border-radius: 16px; display: grid; place-items: center;
  background: var(--soft); color: var(--accent);
}
.cat-icon svg { width: 30px; height: 30px; }
.cat-card h3 { font-size: 24px; font-weight: 800; letter-spacing: -0.02em; }
.cat-card h3 small { margin-left: 8px; font-size: 14px; font-weight: 600; color: var(--text-mute); letter-spacing: 0; }
.cat-card p { color: var(--text-sub); font-size: 15px; }
.tags { display: flex; flex-wrap: wrap; gap: 6px; margin-top: auto; }
.tag { padding: 4px 10px; border-radius: 999px; background: var(--surface); border: 1px solid var(--line); font-size: 13px; color: var(--text-sub); }
.cat-arrow {
  position: absolute; top: 32px; right: 32px; width: 36px; height: 36px; border-radius: 50%;
  display: grid; place-items: center; border: 1px solid var(--line); color: var(--text-mute); transition: all .2s;
}
.cat-card:hover .cat-arrow { background: var(--accent); border-color: var(--accent); color: #fff; }

/* ---------- Features ---------- */
.features { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.feature { padding: 28px; border-radius: var(--radius); background: var(--surface); }
.feature b { display: block; font-size: 17px; margin-bottom: 6px; }
.feature span { font-size: 15px; color: var(--text-sub); }

/* ---------- Category page ---------- */
.page-hero { padding: 64px 0 32px; }
.page-hero .crumb { font-size: 14px; color: var(--text-mute); margin-bottom: 16px; }
.page-hero .crumb a:hover { color: var(--text); }
.page-hero h1 { display: flex; align-items: center; gap: 16px; font-size: clamp(32px, 5vw, 44px); font-weight: 800; letter-spacing: -0.03em; }
.page-hero p { margin-top: 12px; color: var(--text-sub); font-size: 17px; max-width: 640px; }

.filters { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 24px; }
.filter {
  padding: 8px 16px; border-radius: 999px; border: 1px solid var(--line); background: var(--bg);
  font: inherit; font-size: 14px; font-weight: 500; color: var(--text-sub); cursor: pointer;
}
.filter.active { background: var(--text); border-color: var(--text); color: #fff; }

.exp-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.exp-card {
  display: flex; flex-direction: column; gap: 10px; padding: 24px; min-height: 180px;
  border: 1px solid var(--line); border-radius: 16px; background: var(--bg); transition: border-color .2s, box-shadow .2s;
}
.exp-card:hover { border-color: var(--line-strong); box-shadow: 0 10px 30px rgba(0,0,0,.05); }
.exp-card .topic { font-size: 12px; font-weight: 700; color: var(--accent, var(--text-mute)); letter-spacing: .02em; }
.exp-card h4 { font-size: 18px; font-weight: 700; letter-spacing: -0.01em; }
.exp-card p { font-size: 14px; color: var(--text-sub); }
.exp-card .meta { margin-top: auto; display: flex; justify-content: space-between; font-size: 13px; color: var(--text-mute); }
.badge-soon { padding: 2px 8px; border-radius: 6px; background: var(--surface); border: 1px solid var(--line); font-size: 12px; }

/* ---------- Footer ---------- */
.site-footer { border-top: 1px solid var(--line); padding: 32px 0; font-size: 14px; color: var(--text-mute); }
.site-footer .container { display: flex; justify-content: space-between; gap: 16px; flex-wrap: wrap; }

/* ---------- Responsive ---------- */
@media (max-width: 860px) {
  .categories, .features { grid-template-columns: 1fr; }
  .exp-grid { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 600px) {
  .container { padding: 0 16px; }
  .hero { padding: 64px 0 48px; }
  .cat-card { padding: 24px; min-height: 0; }
  .cat-arrow { top: 24px; right: 24px; }
  .exp-grid { grid-template-columns: 1fr; }
  .section-head { flex-direction: column; align-items: start; }
}