/* ============================================================
   AP Physics 1 vs Physics C — 비교 가이드
   Design concept: 공학 도면(Blueprint / Schematic) 미학
   ============================================================ */

@import url('https://cdn.jsdelivr.net/gh/orioncactus/pretendard@v1.3.9/dist/web/variable/pretendardvariable-dynamic-subset.css');
@import url('https://fonts.googleapis.com/css2?family=JetBrains+Mono:ital,wght@0,400;0,500;0,600;0,700;1,400&display=swap');

:root{
  /* --- Color tokens --- */
  --blueprint:      #0F3A5F;   /* 메인 도면 남색 배경 */
  --blueprint-deep:  #0A2A45;  /* 더 짙은 남색 (히어로, 푸터) */
  --line-cyan:      #8FC8E8;   /* 도면 선/좌표 색 */
  --line-cyan-dim:  #5C93B8;
  --paper:          #FAF7EF;   /* 본문 종이 배경 */
  --paper-dim:      #F1ECDD;   /* 은은한 그리드/카드 배경 */
  --grid-line:      #E1D9C2;   /* 종이 위 격자선 */
  --ink:            #1C2536;   /* 본문 텍스트 */
  --ink-soft:       #4A5568;   /* 보조 텍스트 */
  --mech-amber:     #E2963A;   /* AP Physics 1 트랙 색 (역학/대수) */
  --calc-teal:      #268C82;   /* AP Physics C 트랙 색 (미적분) */
  --alert:          #D14B2E;   /* 강조/경고 색 */
  --border:         #D8CFB4;

  --font-kr: 'Pretendard Variable', Pretendard, -apple-system, 'Malgun Gothic', sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, monospace;

  --radius: 3px;
}

*,*::before,*::after{ box-sizing:border-box; }
html{ scroll-behavior:smooth; }
body{
  margin:0;
  font-family:var(--font-kr);
  color:var(--ink);
  background:var(--paper);
  line-height:1.72;
  font-size:16.5px;
  -webkit-font-smoothing:antialiased;
}
img{ max-width:100%; display:block; }
a{ color:inherit; }
h1,h2,h3,h4{ font-family:var(--font-kr); font-weight:800; line-height:1.32; margin:0 0 .6em; letter-spacing:-0.01em; }
p{ margin:0 0 1.1em; color:var(--ink); }
ul,ol{ padding-left:1.3em; }
.container{ max-width:1120px; margin:0 auto; padding:0 24px; }

/* ---------------- Grid paper texture ---------------- */
.paper-grid{
  background-image:
    linear-gradient(var(--grid-line) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid-line) 1px, transparent 1px);
  background-size:34px 34px;
  background-position:-1px -1px;
}

/* ---------------- Eyebrow / mono labels ---------------- */
.eyebrow{
  display:inline-flex; align-items:center; gap:8px;
  font-family:var(--font-mono);
  font-size:12.5px;
  letter-spacing:.14em;
  text-transform:uppercase;
  color:var(--line-cyan-dim);
  font-weight:600;
}
.eyebrow::before{ content:''; width:18px; height:1px; background:currentColor; display:inline-block; }
.on-paper .eyebrow{ color:var(--calc-teal); }
.on-paper .eyebrow::before{ background:var(--calc-teal); }

/* ---------------- Header (title block 스타일) ---------------- */
.site-header{
  position:sticky; top:0; z-index:100;
  background:var(--blueprint-deep);
  border-bottom:2px solid var(--line-cyan-dim);
}
.header-inner{
  display:flex; align-items:center; justify-content:space-between;
  padding:14px 24px;
  max-width:1120px; margin:0 auto;
}
.brand{
  display:flex; align-items:center; gap:12px;
  text-decoration:none; color:#fff;
}
.brand-mark{
  width:38px; height:38px; flex:0 0 auto;
  border:1.5px solid var(--line-cyan);
  border-radius:2px;
  display:flex; align-items:center; justify-content:center;
  font-family:var(--font-mono); font-weight:700; font-size:11px;
  color:var(--line-cyan);
  position:relative;
}
.brand-mark::after{
  content:''; position:absolute; inset:4px;
  border:1px dashed var(--line-cyan-dim);
}
.brand-text{ display:flex; flex-direction:column; line-height:1.25; }
.brand-text strong{ font-size:15.5px; font-weight:800; letter-spacing:-.01em; }
.brand-text span{ font-family:var(--font-mono); font-size:10.5px; color:var(--line-cyan-dim); letter-spacing:.08em; }

.main-nav{ display:flex; gap:2px; }
.main-nav a{
  text-decoration:none; color:#DCE9F2;
  font-size:14.5px; font-weight:600;
  padding:10px 14px; border-radius:2px;
  position:relative;
  transition:color .15s ease, background .15s ease;
}
.main-nav a:hover, .main-nav a.active{ color:#fff; background:rgba(143,200,232,.12); }
.main-nav a.active::after{
  content:''; position:absolute; left:14px; right:14px; bottom:5px; height:2px; background:var(--mech-amber);
}
.nav-toggle{
  display:none; background:none; border:1px solid var(--line-cyan-dim); color:#fff;
  width:40px; height:36px; border-radius:2px; cursor:pointer;
}

/* ---------------- Hero ---------------- */
.hero{
  background:
    radial-gradient(ellipse at 15% 0%, rgba(143,200,232,.14), transparent 55%),
    var(--blueprint);
  color:#fff;
  position:relative;
  overflow:hidden;
  border-bottom:1px solid var(--line-cyan-dim);
}
.hero::before{
  content:'';
  position:absolute; inset:0;
  background-image:
    linear-gradient(rgba(143,200,232,.09) 1px, transparent 1px),
    linear-gradient(90deg, rgba(143,200,232,.09) 1px, transparent 1px);
  background-size:44px 44px;
  pointer-events:none;
}
.hero-inner{
  position:relative; z-index:1;
  max-width:1120px; margin:0 auto;
  padding:72px 24px 56px;
}
.hero .eyebrow{ color:var(--line-cyan); margin-bottom:18px; }
.hero .eyebrow::before{ background:var(--line-cyan); }
.hero h1{
  font-size:clamp(30px, 4.4vw, 50px);
  color:#fff; max-width:16ch; margin-bottom:.42em;
}
.hero h1 em{ font-style:normal; color:var(--mech-amber); }
.hero-sub{
  font-size:17.5px; color:#C9DCEA; max-width:56ch; margin-bottom:30px;
}
.hero-meta{
  display:flex; flex-wrap:wrap; gap:10px 22px;
  font-family:var(--font-mono); font-size:12.5px; color:var(--line-cyan-dim);
  margin-bottom:34px;
}
.hero-meta b{ color:var(--line-cyan); font-weight:600; }
.hero-ctas{ display:flex; gap:12px; flex-wrap:wrap; }

.btn{
  display:inline-flex; align-items:center; gap:8px;
  font-weight:700; font-size:14.5px;
  padding:13px 22px; border-radius:2px;
  text-decoration:none; cursor:pointer; border:1.5px solid transparent;
  transition:transform .12s ease, background .15s ease, border-color .15s ease;
}
.btn:hover{ transform:translateY(-1px); }
.btn-primary{ background:var(--mech-amber); color:#1C2536; }
.btn-primary:hover{ background:#EDA95A; }
.btn-outline{ background:transparent; border-color:var(--line-cyan-dim); color:#fff; }
.btn-outline:hover{ border-color:var(--line-cyan); background:rgba(143,200,232,.08); }
.btn-on-paper{ background:var(--calc-teal); color:#fff; }
.btn-on-paper:hover{ background:#2AA294; }

/* ---------------- Trajectory diagram (signature element) ---------------- */
.trajectory-wrap{
  margin-top:46px; border:1px solid var(--line-cyan-dim);
  background:rgba(10,42,69,.4);
  padding:22px 22px 10px;
  border-radius:2px;
}
.trajectory-wrap svg{ width:100%; height:auto; display:block; }
.trajectory-caption{
  display:flex; justify-content:space-between; flex-wrap:wrap; gap:10px;
  font-family:var(--font-mono); font-size:11.5px; color:var(--line-cyan-dim);
  padding:10px 2px 4px; border-top:1px dashed var(--line-cyan-dim); margin-top:14px;
}

/* ---------------- Sections on paper ---------------- */
.section{ padding:68px 0; }
.section-tight{ padding:44px 0; }
.section-head{ max-width:70ch; margin-bottom:38px; }
.section-head h2{ font-size:clamp(24px,3vw,34px); }
.section-head p{ color:var(--ink-soft); font-size:16px; }
.on-blueprint{ background:var(--blueprint-deep); color:#fff; }
.on-blueprint h2{ color:#fff; }
.on-blueprint p{ color:#C9DCEA; }
.on-dim{ background:var(--paper-dim); }

/* ---------------- Comparison table (schematic panel) ---------------- */
.panel{
  border:1px solid var(--border); background:#fff;
  border-radius:2px; position:relative;
}
.panel-corner{
  position:absolute; width:12px; height:12px;
  border:1.5px solid var(--calc-teal);
}
.panel-corner.tl{ top:-1px; left:-1px; border-right:none; border-bottom:none; }
.panel-corner.tr{ top:-1px; right:-1px; border-left:none; border-bottom:none; }
.panel-corner.bl{ bottom:-1px; left:-1px; border-right:none; border-top:none; }
.panel-corner.br{ bottom:-1px; right:-1px; border-left:none; border-top:none; }

.compare-table{ width:100%; border-collapse:collapse; font-size:15px; }
.compare-table caption{ text-align:left; font-family:var(--font-mono); font-size:12px; color:var(--ink-soft); padding:14px 18px 0; }
.compare-table th, .compare-table td{
  padding:14px 18px; text-align:left; border-bottom:1px solid var(--grid-line);
  vertical-align:top;
}
.compare-table thead th{
  font-family:var(--font-mono); font-size:12px; letter-spacing:.04em;
  text-transform:uppercase; color:#fff; background:var(--blueprint);
  position:sticky; top:64px;
}
.compare-table thead th.col-mech{ background:var(--mech-amber); color:#1C2536; }
.compare-table thead th.col-calc{ background:var(--calc-teal); }
.compare-table tbody th{ font-weight:700; background:var(--paper-dim); width:18%; font-size:14px; }
.compare-table tbody tr:last-child td, .compare-table tbody tr:last-child th{ border-bottom:none; }
.tag{
  display:inline-block; font-family:var(--font-mono); font-size:11px; font-weight:700;
  padding:2px 8px; border-radius:20px; letter-spacing:.02em;
}
.tag-mech{ background:rgba(226,150,58,.16); color:#9A5D14; }
.tag-calc{ background:rgba(38,140,130,.14); color:#1B6B62; }

/* ---------------- Cards ---------------- */
.grid-2{ display:grid; grid-template-columns:1fr 1fr; gap:22px; }
.grid-3{ display:grid; grid-template-columns:repeat(3,1fr); gap:20px; }
.card{
  background:#fff; border:1px solid var(--border); border-radius:2px;
  padding:26px 24px;
}
.card h3{ font-size:18.5px; margin-bottom:10px; }
.card p{ color:var(--ink-soft); font-size:15px; margin-bottom:0; }
.card-mech{ border-top:3px solid var(--mech-amber); }
.card-calc{ border-top:3px solid var(--calc-teal); }

.track-card{
  background:#fff; border:1px solid var(--border); border-radius:2px; overflow:hidden;
}
.track-head{ padding:22px 24px 18px; color:#fff; }
.track-head.mech{ background:linear-gradient(135deg,var(--mech-amber),#C9791E); }
.track-head.calc{ background:linear-gradient(135deg,var(--calc-teal),#154F49); }
.track-head .eyebrow{ color:rgba(255,255,255,.85); }
.track-head .eyebrow::before{ background:rgba(255,255,255,.85); }
.track-head h3{ color:#fff; font-size:22px; margin:6px 0 4px; }
.track-head p{ color:rgba(255,255,255,.9); margin:0; font-size:14.5px; }
.track-body{ padding:22px 24px; }
.track-body ul{ margin:0 0 16px; padding-left:1.2em; font-size:15px; color:var(--ink-soft); }
.track-body li{ margin-bottom:6px; }
.track-stat{
  display:flex; justify-content:space-between; padding:9px 0;
  border-top:1px dashed var(--grid-line); font-size:14.5px;
}
.track-stat b{ font-family:var(--font-mono); font-size:14px; }

/* ---------------- FAQ ---------------- */
.faq-item{ border-bottom:1px solid var(--grid-line); }
.faq-q{
  width:100%; text-align:left; background:none; border:none; cursor:pointer;
  padding:20px 4px; font-size:16.5px; font-weight:700; color:var(--ink);
  display:flex; justify-content:space-between; align-items:center; gap:16px;
  font-family:var(--font-kr);
}
.faq-q::after{
  content:'+'; font-family:var(--font-mono); font-size:20px; color:var(--calc-teal);
  flex:0 0 auto; transition:transform .18s ease;
}
.faq-item.open .faq-q::after{ transform:rotate(45deg); }
.faq-a{ max-height:0; overflow:hidden; transition:max-height .25s ease; }
.faq-item.open .faq-a{ max-height:600px; }
.faq-a-inner{ padding:0 4px 22px; color:var(--ink-soft); font-size:15.3px; }

/* ---------------- Steps / numbered ---------------- */
.steps{ counter-reset:step; list-style:none; padding:0; margin:0; }
.steps li{
  counter-increment:step; position:relative; padding:0 0 26px 52px; margin-bottom:0;
}
.steps li::before{
  content:counter(step,decimal-leading-zero);
  position:absolute; left:0; top:0;
  font-family:var(--font-mono); font-weight:700; font-size:13px; color:var(--blueprint);
  width:36px; height:36px; border:1.5px solid var(--blueprint);
  border-radius:50%; display:flex; align-items:center; justify-content:center;
}
.steps li::after{
  content:''; position:absolute; left:17px; top:36px; bottom:0; width:1px;
  border-left:1px dashed var(--border);
}
.steps li:last-child::after{ display:none; }
.steps h4{ font-size:16.5px; margin-bottom:4px; }
.steps p{ font-size:14.8px; color:var(--ink-soft); margin-bottom:0; }

/* ---------------- Quiz widget ---------------- */
.quiz{
  background:var(--blueprint-deep); color:#fff; border-radius:2px;
  padding:34px; border:1px solid var(--line-cyan-dim);
}
.quiz h3{ color:#fff; font-size:21px; }
.quiz-lead{ color:#C9DCEA; font-size:14.5px; margin-bottom:22px; }
.quiz-q{ margin-bottom:20px; }
.quiz-q-label{ font-family:var(--font-mono); font-size:12px; color:var(--line-cyan); margin-bottom:10px; letter-spacing:.05em; }
.quiz-opts{ display:grid; grid-template-columns:1fr 1fr; gap:10px; }
.quiz-opt{
  background:rgba(255,255,255,.04); border:1px solid var(--line-cyan-dim);
  color:#fff; text-align:left; padding:12px 14px; border-radius:2px; cursor:pointer;
  font-family:var(--font-kr); font-size:14px; transition:background .15s ease, border-color .15s ease;
}
.quiz-opt:hover{ background:rgba(143,200,232,.1); }
.quiz-opt.selected{ border-color:var(--mech-amber); background:rgba(226,150,58,.14); }
.quiz-result{
  margin-top:22px; padding:20px; border-radius:2px; background:rgba(143,200,232,.08);
  border:1px dashed var(--line-cyan-dim); display:none;
}
.quiz-result.show{ display:block; }
.quiz-result h4{ color:var(--mech-amber); font-size:17px; margin-bottom:8px; }
.quiz-result p{ color:#DCE9F2; font-size:14.5px; margin-bottom:0; }
.quiz-btn-row{ display:flex; gap:10px; margin-top:6px; }

/* ---------------- Callout / note ---------------- */
.callout{
  border-left:3px solid var(--calc-teal);
  background:var(--paper-dim);
  padding:18px 20px; border-radius:0 2px 2px 0; font-size:15px; color:var(--ink-soft);
}
.callout b{ color:var(--ink); }
.callout.warn{ border-left-color:var(--alert); }

/* ---------------- Breadcrumb ---------------- */
.breadcrumb{
  font-family:var(--font-mono); font-size:12px; color:var(--ink-soft);
  padding:16px 0 0;
}
.breadcrumb a{ text-decoration:none; color:var(--calc-teal); }
.breadcrumb span{ margin:0 6px; color:var(--border); }

/* ---------------- Related links / index cluster ---------------- */
.link-grid{ display:grid; grid-template-columns:repeat(3,1fr); gap:16px; }
.link-card{
  display:block; text-decoration:none; background:#fff; border:1px solid var(--border);
  border-radius:2px; padding:20px; transition:border-color .15s ease, transform .12s ease;
}
.link-card:hover{ border-color:var(--calc-teal); transform:translateY(-2px); }
.link-card .eyebrow{ margin-bottom:10px; }
.link-card h3{ font-size:16.5px; margin-bottom:8px; color:var(--ink); }
.link-card p{ font-size:13.8px; color:var(--ink-soft); margin:0; }

/* ---------------- Footer ---------------- */
.site-footer{ background:var(--blueprint-deep); color:#C9DCEA; padding:52px 0 26px; margin-top:70px; }
.footer-grid{ display:grid; grid-template-columns:1.6fr 1fr 1fr 1fr; gap:34px; margin-bottom:34px; }
.footer-grid h4{ color:#fff; font-size:13.5px; font-family:var(--font-mono); letter-spacing:.06em; margin-bottom:14px; }
.footer-grid ul{ list-style:none; padding:0; margin:0; }
.footer-grid li{ margin-bottom:9px; font-size:14px; }
.footer-grid a{ text-decoration:none; color:#C9DCEA; }
.footer-grid a:hover{ color:#fff; }
.footer-bottom{
  border-top:1px solid rgba(143,200,232,.18); padding-top:22px;
  display:flex; justify-content:space-between; flex-wrap:wrap; gap:10px;
  font-size:12.5px; color:var(--line-cyan-dim); font-family:var(--font-mono);
}

/* ---------------- Responsive ---------------- */
@media (max-width: 860px){
  .main-nav{
    position:fixed; inset:60px 0 0 0; background:var(--blueprint-deep);
    flex-direction:column; padding:16px; gap:4px; transform:translateX(100%);
    transition:transform .2s ease; overflow-y:auto;
  }
  .main-nav.open{ transform:translateX(0); }
  .main-nav a{ padding:14px 16px; font-size:16px; }
  .nav-toggle{ display:block; }
  .grid-2, .grid-3, .link-grid{ grid-template-columns:1fr; }
  .footer-grid{ grid-template-columns:1fr 1fr; }
  .compare-table thead th{ position:static; }
  .quiz-opts{ grid-template-columns:1fr; }
  .hero-inner{ padding:52px 20px 40px; }
}

@media (prefers-reduced-motion: reduce){
  *{ animation:none !important; transition:none !important; scroll-behavior:auto !important; }
}