/* 기계학습 2026 — 공통 스타일 (installation / assignment / quiz) */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg:          #f4f6f9;
  --card:        #ffffff;
  --text:        #1e2328;
  --text-light:  #5a6370;
  --accent:      #2563eb;
  --accent-light:#dbeafe;
  --accent-dark: #1d4ed8;
  --ok:          #059669;
  --ok-bg:       #ecfdf5;
  --bad:         #dc2626;
  --bad-bg:      #fef2f2;
  --code-bg:     #1e1e2e;
  --code-text:   #cdd6f4;
  --code-green:  #a6e3a1;
  --border:      #e2e6eb;
  --radius:      12px;
  --shadow:      0 2px 12px rgba(0,0,0,.08);
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Apple SD Gothic Neo', 'Pretendard', 'Malgun Gothic', 'Segoe UI', Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  min-height: 100vh;
  word-break: keep-all;
  overflow-wrap: break-word;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.page-wrapper { max-width: 920px; margin: 0 auto; padding: 0 20px 80px; }

/* ── Hero ── */
.hero {
  background: linear-gradient(135deg, #4f46e5 0%, #2563eb 100%);
  color: #fff;
  border-radius: 0 0 var(--radius) var(--radius);
  padding: 52px 32px 44px;
  text-align: center;
  margin-bottom: 36px;
}
.hero .badge {
  display: inline-block;
  background: rgba(255,255,255,.18);
  border: 1px solid rgba(255,255,255,.3);
  border-radius: 20px;
  padding: 4px 14px;
  font-size: .82rem;
  letter-spacing: .04em;
  margin-bottom: 16px;
}
.hero h1 { font-size: 2.2rem; font-weight: 700; margin-bottom: 10px; letter-spacing: -.02em; }
.hero p  { font-size: 1.05rem; opacity: .9; max-width: 660px; margin: 0 auto; }

/* ── Section titles ── */
.section-title {
  font-size: 1.4rem;
  font-weight: 700;
  margin: 44px 0 8px;
  display: flex;
  align-items: center;
  gap: 10px;
  scroll-margin-top: 16px;
}
.section-sub { color: var(--text-light); font-size: .93rem; margin-bottom: 18px; }

/* ── Cards ── */
.card {
  background: var(--card);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
  overflow: hidden;
  margin-bottom: 22px;
}
.card-header {
  padding: 16px 22px 12px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}
.card-header h3 { font-size: 1.06rem; font-weight: 600; }
.card-body { padding: 18px 22px; }
.card-body p { margin-bottom: 10px; }
.card-body ul, .card-body ol { margin: 6px 0 12px 22px; }
.card-body li { margin-bottom: 4px; }
.card-body h4 { font-size: .98rem; margin: 16px 0 6px; }

.tag {
  display: inline-block;
  font-size: .74rem;
  font-weight: 600;
  padding: 2px 10px;
  border-radius: 999px;
  background: var(--accent-light);
  color: var(--accent-dark);
}

/* ── Prereq grid ── */
.prereq-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(190px, 1fr));
  gap: 12px;
  margin: 16px 0;
}
.prereq-item {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 14px 16px;
  text-align: center;
  box-shadow: var(--shadow);
}
.prereq-item .prereq-icon  { font-size: 1.6rem; margin-bottom: 6px; }
.prereq-item .prereq-label { font-size: .85rem; font-weight: 600; }
.prereq-item .prereq-note  { font-size: .78rem; color: var(--text-light); margin-top: 2px; }

/* ── Steps ── */
.step { display: flex; gap: 18px; margin-bottom: 26px; }
.step:last-child { margin-bottom: 0; }
.step-num {
  flex-shrink: 0;
  width: 36px; height: 36px;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  font-weight: 700;
  font-size: .95rem;
  display: flex; align-items: center; justify-content: center;
}
.step-content { padding-top: 5px; flex: 1; min-width: 0; }
.step-content p { margin-bottom: 10px; }

/* ── Boxes ── */
.info-box, .tip-box, .warn-box {
  border-radius: 8px;
  padding: 12px 16px;
  margin: 12px 0;
  font-size: .91rem;
  display: flex;
  gap: 12px;
  align-items: flex-start;
}
.info-box { background: #eef2ff; border: 1px solid #c7d2fe; }
.tip-box  { background: #ecfdf5; border: 1px solid #6ee7b7; }
.warn-box { background: #fef3c7; border: 1px solid #fcd34d; }
.box-icon { font-size: 1.1rem; flex-shrink: 0; }

/* ── Code ── */
.code-block { background: var(--code-bg); border-radius: 8px; overflow: hidden; margin: 10px 0 14px; }
.code-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 7px 14px; background: #181825;
}
.code-header .lang-tag { font-size: .74rem; color: #7f849c; font-weight: 600; letter-spacing: .04em; }
.copy-btn {
  background: none; border: 1px solid #45475a; color: #bac2de;
  border-radius: 5px; padding: 2px 10px; font-size: .72rem; cursor: pointer;
}
.copy-btn:hover { background: #313244; }
.copy-btn.copied { color: var(--code-green); border-color: var(--code-green); }
pre { padding: 13px 18px; overflow-x: auto; margin: 0; }
pre code {
  font-family: 'SF Mono', 'Fira Code', Consolas, monospace;
  font-size: .84rem; color: var(--code-text); line-height: 1.65;
}
p code, li code, td code, span code, .q-text code, .opt code, .explain code {
  font-family: 'SF Mono', 'Fira Code', Consolas, monospace;
  background: #f1f1f5; color: #c0306f;
  padding: 1px 6px; border-radius: 4px; font-size: .86em;
}
kbd {
  background: #f0f0f0; border: 1px solid #ccc; border-radius: 4px;
  padding: 1px 7px; font-size: .84rem; white-space: nowrap;
}

/* ── Tables ── */
.table-wrap { overflow-x: auto; margin: 10px 0 14px; }
table { border-collapse: collapse; width: 100%; font-size: .9rem; }
th, td { border: 1px solid var(--border); padding: 7px 10px; text-align: left; vertical-align: top; }
th { background: #f1f4f8; font-weight: 600; }

/* ── TOC pills ── */
.toc { display: flex; flex-wrap: wrap; gap: 8px; justify-content: center; margin-bottom: 26px; }
.toc a {
  background: var(--card); border: 1px solid var(--border); border-radius: 999px;
  padding: 6px 14px; font-size: .84rem; color: var(--text); box-shadow: var(--shadow);
}
.toc a:hover { border-color: var(--accent); color: var(--accent); text-decoration: none; }

/* ── Footer ── */
.page-footer {
  text-align: center; color: var(--text-light); font-size: .84rem;
  padding-top: 36px; border-top: 1px solid var(--border); margin-top: 24px;
}

@media (max-width: 600px) {
  .hero { padding: 38px 20px 32px; }
  .hero h1 { font-size: 1.7rem; }
  .card-body, .card-header { padding: 14px 16px; }
  .step { flex-direction: column; gap: 10px; }
}

/* ── 강의 홈으로 돌아가기 버튼 ── */
.hero { position: relative; }
.back-btn {
  position: absolute; top: 14px; left: 16px;
  display: inline-flex; align-items: center; gap: 6px;
  background: rgba(255,255,255,.18); border: 1px solid rgba(255,255,255,.35);
  color: #fff; border-radius: 999px; padding: 5px 14px;
  font-size: .85rem; font-weight: 600;
}
.back-btn:hover { background: rgba(255,255,255,.3); text-decoration: none; }
.hero { padding-top: 64px; }
@media (max-width: 600px) { .hero { padding-top: 60px; } }