/* ============================================================
   MYP Physical & Earth Sciences — Field Notebook stylesheet
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@400;500;600;700&family=Source+Serif+4:opsz,wght@8..60,400;8..60,500;8..60,600&family=IBM+Plex+Mono:wght@400;500&display=swap');

:root{
  --paper: #EAF0EC;
  --paper-2: #E1E9E2;
  --ink: #1C2B22;
  --ink-soft: #445046;
  --line: #C9D3C9;

  --physics: #2E6E9E;
  --physics-soft: #DCE8F1;
  --chem: #7C5A96;
  --chem-soft: #E9E1EF;
  --earth: #B07A3E;
  --earth-soft: #F1E5D3;
  --waves: #2E8F79;
  --waves-soft: #DCEEE8;

  --sun: #E8A33D;
  --card-radius: 14px;
  --max: 880px;
}

*{box-sizing:border-box;}
html{scroll-behavior:smooth;}
body{
  margin:0;
  background:var(--paper);
  color:var(--ink);
  font-family:'Source Serif 4', Georgia, serif;
  line-height:1.65;
  font-size:17px;
  -webkit-font-smoothing:antialiased;
}
h1,h2,h3,.eyebrow,.tab-num,nav a,.btn,.chip,.term{
  font-family:'Space Grotesk', system-ui, sans-serif;
}
code, .formula, .unit-num-big{
  font-family:'IBM Plex Mono', monospace;
}
a{color:inherit;}
img{max-width:100%;}

/* faint ruled-paper texture behind main content */
.page{
  background-image: repeating-linear-gradient(
    to bottom,
    transparent, transparent 37px, var(--line) 38px, transparent 39px
  );
  background-position: 0 140px;
}

/* ---------------- Top bar ---------------- */
.topbar{
  position:sticky; top:0; z-index:40;
  display:flex; align-items:center; justify-content:space-between;
  padding:14px 18px;
  background:rgba(234,240,236,0.92);
  backdrop-filter:blur(6px);
  border-bottom:1px solid var(--line);
}
.brand{
  display:flex; flex-direction:column; gap:0;
  text-decoration:none;
}
.brand-en{font-weight:700; font-size:15px; letter-spacing:0.02em;}
.brand-kr{font-size:11px; color:var(--ink-soft);}
.menu-btn{
  border:1px solid var(--ink);
  background:var(--paper);
  color:var(--ink);
  font-weight:600;
  font-size:14px;
  padding:8px 14px;
  border-radius:100px;
  cursor:pointer;
}
@media(min-width:900px){ .menu-btn{display:none;} }

/* ---------------- Layout shell ---------------- */
.shell{
  display:flex;
  max-width:1180px;
  margin:0 auto;
}
.content-wrap{
  flex:1;
  min-width:0;
}

/* ---------------- Binder tab nav ---------------- */
.tabnav{
  width:236px;
  flex-shrink:0;
  padding:22px 0 40px 18px;
}
@media(max-width:899px){
  .tabnav{
    position:fixed; inset:0 20% 0 0;
    z-index:60;
    background:var(--paper);
    padding:70px 16px 20px 16px;
    overflow-y:auto;
    transform:translateX(-105%);
    transition:transform .28s ease;
    box-shadow:2px 0 24px rgba(0,0,0,0.15);
  }
  .tabnav.open{transform:translateX(0);}
  .scrim{
    position:fixed; inset:0; z-index:55;
    background:rgba(20,30,24,0.35);
    display:none;
  }
  .scrim.open{display:block;}
}
.tabnav-close{
  display:none;
  border:none;background:none;font-size:26px;
  position:absolute; top:16px; right:16px;
  cursor:pointer; color:var(--ink);
}
@media(max-width:899px){ .tabnav-close{display:block;} }

.tab-group-label{
  font-size:11px; text-transform:uppercase; letter-spacing:0.12em;
  color:var(--ink-soft); margin:18px 0 6px 4px;
}
.tab-group-label:first-child{margin-top:0;}

.tab{
  display:flex; align-items:center; gap:10px;
  padding:9px 12px 9px 14px;
  margin-bottom:6px;
  text-decoration:none;
  color:var(--ink);
  font-size:14px;
  font-weight:500;
  border-radius:3px 10px 10px 3px;
  border-left:4px solid var(--tabcolor, var(--ink));
  background:transparent;
  position:relative;
}
.tab:hover{background:rgba(255,255,255,0.55);}
.tab.active{
  background:#fff;
  box-shadow:0 1px 0 rgba(0,0,0,0.04);
  font-weight:700;
}
.tab-num{
  font-size:11px;
  color:#fff;
  background:var(--tabcolor, var(--ink));
  width:20px;height:20px;
  border-radius:5px;
  display:flex;align-items:center;justify-content:center;
  flex-shrink:0;
}
.tab-en{display:block;}
.tab-kr{display:block; font-size:11px; color:var(--ink-soft); font-weight:400;}

.tabnav-footer{
  margin-top:22px; padding:12px 12px;
  font-size:12px; color:var(--ink-soft);
  border-top:1px dashed var(--line);
}

/* ---------------- Hero ---------------- */
.hero{
  padding:38px 22px 20px;
  max-width:var(--max);
}
.eyebrow{
  display:inline-flex; align-items:center; gap:8px;
  font-size:12px; font-weight:600; letter-spacing:0.1em; text-transform:uppercase;
  color:var(--tabcolor, var(--ink));
  border:1px solid var(--tabcolor, var(--ink));
  padding:4px 10px 4px 8px;
  border-radius:100px;
  margin-bottom:14px;
}
.eyebrow .dot{width:8px;height:8px;border-radius:50%;background:var(--tabcolor, var(--ink));}
h1{
  font-size:clamp(28px,5vw,42px);
  line-height:1.12;
  margin:0 0 6px;
  letter-spacing:-0.01em;
}
.kr-title{
  font-size:16px; color:var(--ink-soft); margin:0 0 18px;
}
.hook{
  font-size:18px; max-width:62ch;
}

/* ---------------- Content blocks ---------------- */
main.content{
  max-width:var(--max);
  padding:6px 22px 80px;
}
.bigidea{
  background:#fff;
  border-radius:var(--card-radius);
  border:1px solid var(--line);
  border-left:6px solid var(--tabcolor, var(--ink));
  padding:18px 20px;
  margin:18px 0 34px;
}
.bigidea .label{
  font-family:'Space Grotesk',sans-serif; font-size:12px; font-weight:700;
  letter-spacing:0.08em; text-transform:uppercase; color:var(--tabcolor,var(--ink));
  margin-bottom:6px; display:block;
}

.concept{
  position:relative;
  margin:0 0 40px;
  padding-left:20px;
  border-left:3px solid var(--linecolor,var(--line));
}
.concept h2{
  font-size:22px; margin:0 0 4px; display:flex; align-items:baseline; gap:10px;
}
.concept h2 .num{
  font-family:'IBM Plex Mono',monospace; font-size:14px; color:#fff;
  background:var(--tabcolor,var(--ink)); padding:2px 8px; border-radius:6px;
}
.concept p{margin:8px 0;}
.concept .formula{
  display:inline-block; background:var(--tabsoft,#eee); border-radius:8px;
  padding:8px 14px; font-size:15px; margin:8px 0; font-weight:500;
}
.concept ul{margin:8px 0; padding-left:22px;}
.concept .example{
  font-size:15px; color:var(--ink-soft); border-top:1px dashed var(--line);
  margin-top:12px; padding-top:10px;
}
.concept .example b{color:var(--ink);}

/* vocab table */
.vocab{
  width:100%; border-collapse:collapse; margin:14px 0 36px;
  font-size:15px;
}
.vocab caption{
  text-align:left; font-family:'Space Grotesk',sans-serif; font-weight:700;
  font-size:13px; text-transform:uppercase; letter-spacing:0.08em;
  color:var(--ink-soft); margin-bottom:8px;
}
.vocab th{
  text-align:left; font-family:'Space Grotesk',sans-serif; font-size:12px;
  text-transform:uppercase; letter-spacing:0.06em; color:var(--ink-soft);
  padding:8px 10px; border-bottom:2px solid var(--ink);
}
.vocab td{padding:9px 10px; border-bottom:1px solid var(--line); vertical-align:top;}
.vocab tr:nth-child(even) td{background:rgba(255,255,255,0.5);}

/* quick check */
.quickcheck{
  background:var(--paper-2);
  border-radius:var(--card-radius);
  padding:16px 18px 8px;
  margin:0 0 40px;
}
.quickcheck > .label{
  font-family:'Space Grotesk',sans-serif; font-weight:700; font-size:13px;
  text-transform:uppercase; letter-spacing:0.08em; margin-bottom:10px; display:block;
  color:var(--tabcolor,var(--ink));
}
.quickcheck details{
  background:#fff; border-radius:10px; padding:10px 14px; margin-bottom:10px;
  border:1px solid var(--line);
}
.quickcheck summary{
  cursor:pointer; font-weight:600; font-size:15px;
}
.quickcheck summary::-webkit-details-marker{color:var(--tabcolor,var(--ink));}
.quickcheck .answer{
  margin-top:8px; padding-top:8px; border-top:1px dashed var(--line);
  font-size:15px; color:var(--ink-soft);
}

/* prev/next */
.pagenav{
  display:flex; justify-content:space-between; gap:14px;
  margin-top:30px; padding-top:20px; border-top:1px solid var(--line);
}
.pagenav a{
  flex:1; text-decoration:none; border:1px solid var(--line); border-radius:12px;
  padding:14px 16px; display:block; background:#fff;
}
.pagenav .dir{font-size:11px; text-transform:uppercase; letter-spacing:0.08em; color:var(--ink-soft); display:block;}
.pagenav .title{font-weight:700; margin-top:2px;}
.pagenav .next{text-align:right;}

footer.site{
  max-width:var(--max); margin:0 auto; padding:20px 22px 60px;
  font-size:13px; color:var(--ink-soft);
}

/* ---------------- Home page ---------------- */
.home-hero{
  max-width:1000px; margin:0 auto; padding:50px 22px 10px;
}
.home-hero h1{font-size:clamp(32px,6vw,54px);}
.home-hero p.lead{font-size:19px; max-width:60ch; color:var(--ink-soft);}
.search-box{
  max-width:1000px; margin:18px auto 8px; padding:0 22px;
}
.search-box input{
  width:100%; padding:13px 16px; font-size:16px;
  border:1.5px solid var(--ink); border-radius:100px;
  font-family:'Source Serif 4',serif; background:#fff;
}
.grid{
  max-width:1000px; margin:26px auto 60px; padding:0 22px;
  display:grid; grid-template-columns:repeat(auto-fill,minmax(260px,1fr));
  gap:16px;
}
.card{
  background:#fff; border:1px solid var(--line); border-radius:var(--card-radius);
  border-top:6px solid var(--tabcolor,var(--ink));
  padding:16px 18px; text-decoration:none; color:var(--ink);
  display:flex; flex-direction:column; gap:6px;
}
.card .cardnum{
  font-family:'IBM Plex Mono',monospace; font-size:13px; color:var(--tabcolor,var(--ink)); font-weight:600;
}
.card .cardtitle{font-weight:700; font-size:17px;}
.card .cardkr{font-size:13px; color:var(--ink-soft);}
.card .cardhook{font-size:14px; color:var(--ink-soft); margin-top:4px;}
.card[hidden]{display:none;}

.groups-legend{
  max-width:1000px; margin:0 auto; padding:0 22px; display:flex; flex-wrap:wrap; gap:10px 18px;
  font-size:13px; color:var(--ink-soft);
}
.groups-legend span.sw{
  display:inline-block; width:10px; height:10px; border-radius:3px; margin-right:6px; vertical-align:middle;
}

/* focus visibility */
a:focus-visible, button:focus-visible, summary:focus-visible{
  outline:2px solid var(--ink); outline-offset:2px;
}

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