:root {
  --navy: #071d34;
  --navy-2: #123b5c;
  --ink: #10263b;
  --muted: #617487;
  --silver: #d7e0e7;
  --paper: #f4f7f9;
  --white: #fff;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  background:
    radial-gradient(circle at 82% 8%, rgba(177, 194, 207, .34), transparent 29rem),
    linear-gradient(180deg, #fbfcfd 0, var(--paper) 38rem);
  font-family: "Pretendard", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}
a { color: inherit; text-decoration: none; }
img { display: block; max-width: 100%; }

.course-topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  border-bottom: 1px solid rgba(164, 181, 194, .74);
  background: rgba(255, 255, 255, .92);
  backdrop-filter: blur(18px);
}
.course-topbar__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  width: min(1480px, calc(100% - 40px));
  margin: 0 auto;
  min-height: 72px;
}
.course-brand { display: flex; align-items: center; gap: 12px; font-weight: 900; }
.course-brand img { width: 44px; height: 44px; border: 1px solid #b7c5d0; border-radius: 14px; }
.course-brand small {
  display: block;
  margin-bottom: 3px;
  color: #6d8193;
  font: 800 9px/1 "Lexend", sans-serif;
  letter-spacing: 1.8px;
  text-transform: uppercase;
}
.course-back {
  display: inline-flex;
  align-items: center;
  min-height: 42px;
  padding: 0 17px;
  border: 1px solid #a4b4c1;
  border-radius: 999px;
  background: #fff;
  font-size: 13px;
  font-weight: 900;
}
.course-back:hover { border-color: var(--navy); background: var(--navy); color: #fff; }

.course-shell { width: min(1480px, calc(100% - 40px)); margin: 0 auto; padding: 32px 0 72px; }
.course-hero {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, .95fr) minmax(420px, 1.05fr);
  min-height: 430px;
  overflow: hidden;
  border: 1px solid #afbfcb;
  border-radius: 32px;
  background: #fff;
  box-shadow: 0 28px 70px -52px rgba(7, 29, 52, .95);
}
.course-hero__copy { display: flex; flex-direction: column; justify-content: center; padding: clamp(30px, 5vw, 74px); }
.course-kicker {
  color: #5c7690;
  font: 800 10px/1 "Lexend", sans-serif;
  letter-spacing: 2.3px;
  text-transform: uppercase;
}
.course-hero h1 {
  margin: 15px 0 18px;
  color: var(--navy);
  font-size: clamp(42px, 5.1vw, 76px);
  line-height: .98;
  letter-spacing: -.055em;
  word-break: keep-all;
}
.course-hero__copy > p { max-width: 650px; margin: 0; color: var(--muted); font-size: 17px; line-height: 1.8; word-break: keep-all; }
.course-meta { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 24px; }
.course-meta span { padding: 8px 11px; border: 1px solid #bdcad4; border-radius: 999px; background: #f7f9fb; font-size: 12px; font-weight: 800; }
.course-hero__image { position: relative; min-height: 360px; background: var(--navy); }
.course-hero__image::after { content: ""; position: absolute; inset: 0; background: linear-gradient(90deg, rgba(7, 29, 52, .25), transparent 36%); pointer-events: none; }
.course-hero__image img { width: 100%; height: 100%; object-fit: cover; }
.course-actions { display: grid; gap: 10px; margin-top: 18px; }
.course-start,
.course-print {
  display: inline-flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  width: 100%;
  padding: 22px 25px;
  border-radius: 20px;
  transition: transform .18s ease, background .18s ease, border-color .18s ease;
}
.course-start {
  background: linear-gradient(135deg, var(--navy), #17466b);
  color: #fff;
  box-shadow: 0 20px 40px -30px rgba(7, 29, 52, .95);
}
.course-print {
  border: 2px solid #d3a72c;
  background: #fff9df;
  color: var(--navy);
  box-shadow: 0 16px 32px -28px rgba(7, 29, 52, .9);
}
.course-start span,
.course-print span { display: grid; gap: 4px; }
.course-start small,
.course-print small { font: 800 9px "Lexend", sans-serif; letter-spacing: 1.6px; text-transform: uppercase; }
.course-start small { color: #b9cddd; }
.course-print small { color: #806515; }
.course-start strong,
.course-print strong { font-size: 21px; }
.course-start b,
.course-print b { font-size: 24px; }
.course-start:hover { background: #0e3555; transform: translateY(-2px); }
.course-print:hover { border-color: #9f7a0c; background: #fff1b6; transform: translateY(-2px); }

.course-intro {
  display: grid;
  grid-template-columns: .72fr 1.28fr;
  gap: 18px;
  margin: 34px 0 18px;
}
.course-intro > div { padding: 28px; border: 1px solid var(--silver); border-radius: 22px; background: rgba(255, 255, 255, .88); }
.course-intro small { color: #668096; font: 800 9px "Lexend", sans-serif; letter-spacing: 1.8px; text-transform: uppercase; }
.course-intro h2 { margin: 9px 0 0; color: var(--navy); font-size: clamp(27px, 3vw, 40px); letter-spacing: -.045em; }
.course-intro p { margin: 0; color: var(--muted); font-size: 15px; line-height: 1.8; word-break: keep-all; }

.lesson-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 13px; }
.lesson-card {
  position: relative;
  display: flex;
  flex-direction: column;
  min-height: 186px;
  padding: 23px;
  overflow: hidden;
  border: 1px solid #cbd6df;
  border-radius: 20px;
  background: rgba(255, 255, 255, .92);
  transition: transform .18s ease, border-color .18s ease, box-shadow .18s ease;
}
.lesson-card::after { content: "↗"; position: absolute; top: 20px; right: 21px; color: #7890a4; font-size: 17px; }
.lesson-card:hover { transform: translateY(-4px); border-color: #718aa0; box-shadow: 0 24px 42px -36px rgba(7, 29, 52, .9); }
.lesson-card__no { color: #557691; font: 800 10px "Lexend", sans-serif; letter-spacing: 1.5px; }
.lesson-card h3 { max-width: calc(100% - 24px); margin: 21px 0 9px; color: var(--navy); font-size: 20px; line-height: 1.28; letter-spacing: -.035em; word-break: keep-all; }
.lesson-card p { margin: 0; color: var(--muted); font-size: 14px; line-height: 1.65; word-break: keep-all; }
.lesson-card strong { margin-top: auto; padding-top: 16px; color: #315674; font-size: 12px; }
.lesson-card--primary { grid-column: span 2; min-height: 220px; border-color: #426786; background: linear-gradient(145deg, #0a2742, #173f60); color: #fff; }
.lesson-card--primary .lesson-card__no, .lesson-card--primary p { color: #bed0de; }
.lesson-card--primary h3, .lesson-card--primary strong { color: #fff; }
.lesson-card--primary::after { color: #fff; }
.lesson-card--notice { cursor: default; background: #e9eef2; }
.lesson-card--notice::after { content: "✓"; }
.lesson-card--notice:hover { transform: none; box-shadow: none; }

.course-bottom { margin-top: 22px; padding: 21px 24px; border: 1px solid #c2cfd9; border-radius: 19px; background: #fff; color: var(--muted); font-size: 14px; line-height: 1.7; text-align: center; }
.course-bottom a { color: var(--navy); font-weight: 900; text-decoration: underline; text-underline-offset: 3px; }

body.reference-page .course-hero { grid-template-columns: 1fr; min-height: auto; }
body.reference-page .course-hero__copy { padding: clamp(34px, 6vw, 78px); }
body.reference-page .course-hero h1 { max-width: 900px; }
.reference-grid { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 13px; margin-top: 26px; }
.reference-card { position: relative; min-height: 270px; overflow: hidden; border: 1px solid #b9c7d2; border-radius: 22px; background: #172d40; color: #fff; isolation: isolate; }
.reference-card::before { content: ""; position: absolute; inset: 0; z-index: -2; background: var(--image) center/cover no-repeat; transition: transform .3s ease; }
.reference-card::after { content: ""; position: absolute; inset: 0; z-index: -1; background: linear-gradient(180deg, rgba(4, 18, 32, .05), rgba(4, 18, 32, .94)); }
.reference-card:hover::before { transform: scale(1.04); }
.reference-card span { position: absolute; left: 21px; right: 21px; bottom: 21px; }
.reference-card strong { display: block; font-size: 20px; }
.reference-card small { display: block; margin-top: 7px; color: #c9d8e4; font-size: 12px; line-height: 1.55; }

@media (max-width: 1050px) {
  .course-hero { grid-template-columns: 1fr; }
  .course-hero__image { min-height: 330px; }
  .lesson-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .reference-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 680px) {
  .course-topbar__inner, .course-shell { width: min(100% - 24px, 1480px); }
  .course-topbar__inner { min-height: 62px; }
  .course-brand img { width: 38px; height: 38px; }
  .course-brand small { display: none; }
  .course-back { min-height: 38px; padding: 0 13px; font-size: 12px; }
  .course-shell { padding-top: 15px; }
  .course-hero { border-radius: 23px; }
  .course-hero__copy { padding: 28px 23px; }
  .course-hero h1 { font-size: clamp(38px, 13vw, 58px); }
  .course-hero__copy > p { font-size: 15px; }
  .course-hero__image { min-height: 230px; }
  .course-start, .course-print { padding: 18px 19px; }
  .course-intro { grid-template-columns: 1fr; margin-top: 22px; }
  .course-intro > div { padding: 22px; }
  .lesson-grid, .reference-grid { grid-template-columns: 1fr; }
  .lesson-card--primary { grid-column: auto; }
  .reference-card { min-height: 230px; }
}