:root{
  --bg:#f5f1ea;
  --card:#ffffff;
  --ink:#1e1e1e;
  --muted:#656565;
  --line:#d8d0c4;
  --soft:#efe9de;
  --accent:#2f5d7c;
  --accent-soft:#eaf1f6;
  --brown:#7b5a3b;
  --good:#2f6b3d;
  --bad:#8c2f2f;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;
  font-family:Arial, Helvetica, sans-serif;
  background:var(--bg);
  color:var(--ink);
}
.topbar{
  position:sticky;
  top:0;
  z-index:10;
  background:#fff;
  border-bottom:1px solid var(--line);
}
.wrap{
  max-width:1180px;
  margin:0 auto;
  padding:18px;
}
.brand{
  display:flex;
  gap:20px;
  align-items:center;
  justify-content:space-between;
}
.brand h1{margin:0;font-size:26px}
.brand p{margin:4px 0 0;color:var(--muted)}
nav{
  display:flex;
  gap:10px;
  flex-wrap:wrap;
}
nav a{
  text-decoration:none;
  color:var(--ink);
  background:#f4efe7;
  border:1px solid var(--line);
  padding:8px 12px;
  border-radius:10px;
  font-size:14px;
}
nav a.active, nav a:hover{
  background:#e8dfd2;
}
.hero, .panel{
  background:var(--card);
  border:1px solid var(--line);
  border-radius:16px;
  padding:22px;
}
.hero h2, .panel h2, .panel h3, .panel h4{margin-top:0}
.hero p, .panel p, .panel li{line-height:1.55}
.kicker{
  display:inline-block;
  padding:6px 10px;
  border-radius:999px;
  background:var(--soft);
  border:1px solid var(--line);
  font-size:12px;
  margin-bottom:10px;
}
.grid{
  display:grid;
  gap:18px;
}
.grid.cards{
  grid-template-columns:repeat(auto-fit, minmax(230px, 1fr));
}
.grid.two{
  grid-template-columns:repeat(auto-fit, minmax(320px, 1fr));
}
.grid.three{
  grid-template-columns:repeat(auto-fit, minmax(260px, 1fr));
}
.feature{
  background:#fff;
  border:1px solid var(--line);
  border-radius:14px;
  padding:18px;
}
.feature h3{margin:0 0 8px}
.feature p{margin:0;color:var(--muted)}
.cta{
  display:inline-block;
  margin-top:12px;
  padding:10px 14px;
  background:var(--accent);
  color:#fff;
  text-decoration:none;
  border-radius:10px;
}
.spacer{height:18px}
.note-block{
  border-left:4px solid var(--brown);
  padding-left:14px;
  margin:14px 0;
}
.clean{
  margin:8px 0 0 18px;
}
.small{font-size:14px}
.muted{color:var(--muted)}
table{
  width:100%;
  border-collapse:collapse;
}
th, td{
  border:1px solid var(--line);
  padding:10px;
  text-align:left;
  vertical-align:top;
}
th{background:#f3eee5}
.symbol-grid{
  display:grid;
  grid-template-columns:repeat(auto-fit, minmax(180px, 1fr));
  gap:16px;
}
.symbol-card{
  background:#fff;
  border:1px solid var(--line);
  border-radius:16px;
  padding:14px;
  text-align:center;
}
.symbol-card h4{
  margin:10px 0 4px;
  font-size:17px;
}
.symbol-card p{
  margin:0;
  color:var(--muted);
  font-size:14px;
}
svg{
  max-width:100%;
  height:auto;
}
.diagram-card{
  background:#fff;
  border:1px solid var(--line);
  border-radius:16px;
  padding:16px;
}
.diagram-row{
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:18px;
}
@media (max-width:900px){
  .brand{flex-direction:column;align-items:flex-start}
  .diagram-row{grid-template-columns:1fr}
}
.flash-grid{
  display:grid;
  grid-template-columns:repeat(auto-fit, minmax(240px, 1fr));
  gap:16px;
}
.flashcard{
  perspective:1000px;
  height:220px;
}
.flashcard-inner{
  position:relative;
  width:100%;
  height:100%;
  transition:transform .45s;
  transform-style:preserve-3d;
  cursor:pointer;
}
.flashcard.flipped .flashcard-inner{transform:rotateY(180deg)}
.face{
  position:absolute;
  inset:0;
  backface-visibility:hidden;
  border:1px solid var(--line);
  border-radius:16px;
  background:#fff;
  padding:16px;
  display:flex;
  flex-direction:column;
  justify-content:center;
}
.face.back{
  transform:rotateY(180deg);
  background:#fcfaf6;
}
.face .label{
  text-transform:uppercase;
  letter-spacing:.08em;
  color:var(--muted);
  font-size:12px;
}
.face .content{
  font-size:19px;
  line-height:1.4;
  margin-top:10px;
}
.face.center{
  text-align:center;
}
.mindmap-wrap{
  overflow:auto;
  background:#fff;
  border:1px solid var(--line);
  border-radius:16px;
  padding:16px;
}
.quiz-card{
  background:#fff;
  border:1px solid var(--line);
  border-radius:14px;
  padding:18px;
  margin-bottom:16px;
}
.quiz-card h3{font-size:18px}
.option{
  display:block;
  padding:10px 12px;
  margin:8px 0;
  border:1px solid var(--line);
  border-radius:10px;
}
.option input{margin-right:8px}
textarea{
  width:100%;
  padding:10px;
  border:1px solid var(--line);
  border-radius:10px;
  font-family:Arial, Helvetica, sans-serif;
}
button{
  border:none;
  background:var(--accent);
  color:#fff;
  padding:12px 16px;
  border-radius:10px;
  cursor:pointer;
  font-size:15px;
}
button.secondary{
  background:#7a7a7a;
}
.answer-box{
  display:none;
  background:var(--accent-soft);
  border:1px solid #cddce7;
  border-radius:12px;
  padding:12px;
  margin-top:12px;
}
.answer-box.show{display:block}
.score{
  font-size:18px;
  font-weight:bold;
}
.good{color:var(--good)}
.bad{color:var(--bad)}
.practice-box{
  border:2px dashed var(--line);
  border-radius:14px;
  min-height:140px;
  background:#fff;
}
.draw-row{
  display:grid;
  grid-template-columns:220px 1fr;
  gap:16px;
  align-items:center;
  margin-bottom:18px;
}
.blank-strip{
  display:flex;
  gap:10px;
  flex-wrap:wrap;
}
.blank-square{
  width:78px;
  height:78px;
  background:#fff;
  border:1px dashed #bdb3a4;
  border-radius:12px;
}
.callout{
  background:#fbf8f2;
  border:1px solid var(--line);
  border-radius:12px;
  padding:14px;
}
.footer{
  text-align:center;
  color:var(--muted);
  padding:24px 10px 40px;
}