@import url('https://fonts.googleapis.com/css2?family=Sarabun:wght@400;500;600;700;800&display=swap');

:root{
  --purple:#47309a;
  --navy:#111642;
  --gold:#f3b23d;
  --ink:#24243a;
  --muted:#707486;
  --line:#e8e4f4;
  --soft:#f6f2ff;
  --ok:#12965d;
  --bad:#cf3434;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;
  font-family:"Sarabun",system-ui,sans-serif;
  color:var(--ink);
  background:radial-gradient(circle at 50% 0,#f2edff,transparent 32%),linear-gradient(#fff,#fbfaff);
}
.topbar{
  position:sticky;top:0;z-index:20;height:78px;padding:0 7%;
  display:flex;align-items:center;justify-content:space-between;
  background:rgba(255,255,255,.94);backdrop-filter:blur(12px);
  border-bottom:1px solid var(--line)
}
.brand{display:flex;align-items:center;gap:12px}
.brand-logo{
  width:56px;height:56px;border-radius:16px;object-fit:contain;background:white;
  border:1px solid #efe8d2;
  box-shadow:0 10px 24px rgba(17,22,66,.12);
}
.brand span{display:block;color:var(--muted);font-size:13px}
nav{display:flex;gap:18px}
nav a{color:var(--navy);text-decoration:none;font-weight:800}
main{max-width:1120px;margin:auto;padding:32px 20px 70px}
.hero{text-align:center;padding:28px 0 22px}
.pill{
  display:inline-block;padding:8px 18px;border-radius:999px;background:var(--soft);
  color:var(--purple);font-weight:800;letter-spacing:.06em
}
h1{margin:12px 0;color:var(--purple);font-size:clamp(38px,5vw,60px);line-height:1.05}
.subtitle,.lead{color:var(--muted);font-size:19px;text-align:center}
.section{padding:44px 0;scroll-margin-top:96px}
h2{text-align:center;color:var(--purple);font-size:36px;margin:0 0 14px}
.cards{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:24px;margin-top:26px}
.card,.panel{
  background:#fff;border:1px solid var(--line);border-radius:28px;box-shadow:0 18px 50px rgba(27,22,73,.08)
}
.card{overflow:hidden;text-align:left;padding-bottom:26px}
.art{
  height:180px;display:grid;place-items:center;font-size:46px;font-weight:900;color:var(--purple);
  background:linear-gradient(135deg,#ffe3a6,#d9f6ff)
}
.art.dark{background:linear-gradient(135deg,#21104f,#6a46dd);color:#fff2ad}
.card>*:not(.art){margin-left:24px;margin-right:24px}
.tag{display:inline-block;margin-top:22px;padding:6px 14px;border-radius:999px;background:var(--soft);color:var(--purple);font-weight:800}
.card h3{font-size:25px;margin:12px 24px 4px}
.card p{color:var(--muted);line-height:1.6}
.card a{
  display:inline-flex;padding:12px 22px;border-radius:999px;background:var(--purple);color:#fff;text-decoration:none;font-weight:800
}
.equation{display:flex;justify-content:center;align-items:center;gap:10px;flex-wrap:wrap;margin:18px 0;font-size:30px;font-weight:900;color:var(--navy)}
.equation span{min-width:58px;padding:12px;border:3px solid #dfe5f3;border-radius:18px;background:#fbfcff;text-align:center}
.equation small{font-size:22px;color:var(--muted)}
.tip{display:block;max-width:860px;margin:0 auto 22px;padding:12px 18px;border-radius:18px;background:#fff8e8;border:1px solid #ffe1a1;color:#6b4a00;text-align:center}
.hard-note{display:inline-block;margin-left:8px;color:#47309a;font-weight:800}
.game-grid{display:grid;grid-template-columns:.9fr 1.1fr;gap:24px}
.panel{padding:24px}
.panel h3{margin:0 0 14px;color:var(--purple)}
.ball-area{min-height:300px;display:flex;flex-wrap:wrap;align-content:flex-start;gap:12px;padding:14px;border-radius:22px}
.group-list{display:grid;gap:16px}
.group{
  min-height:82px;border:2px dashed #d8d0f2;border-radius:22px;background:#fbfaff;padding:14px;
  display:flex;align-items:center;gap:10px;flex-wrap:wrap;transition:.15s
}
.group strong{width:70px;color:var(--muted)}
.dropzone.dragover,.cell24.dragover{background:#fff9ec;border-color:var(--gold)}
.ball{
  width:46px;height:46px;border-radius:50%;display:grid;place-items:center;
  background:radial-gradient(circle at 30% 25%,#fff6cf,#f2a91f 44%,#e76c23);
  color:#fff;font-weight:900;box-shadow:0 8px 16px rgba(231,108,35,.24);
  cursor:grab;user-select:none
}
.ball.selected{outline:4px solid #3e8cff;transform:scale(1.08)}
.actions{display:flex;justify-content:center;gap:12px;flex-wrap:wrap;margin-top:22px}
button{
  border:0;border-radius:999px;padding:12px 22px;background:var(--purple);color:#fff;
  font-family:inherit;font-size:16px;font-weight:800;cursor:pointer
}
button.secondary{background:#f0edf9;color:var(--purple)}
button:disabled{background:#ebe8f3;color:#9a96aa;cursor:not-allowed}
.feedback{text-align:center;color:var(--purple);font-size:20px;font-weight:800;min-height:32px}
.feedback.ok{color:var(--ok)} .feedback.bad{color:var(--bad)}
.wide{max-width:1000px;margin:auto}
.center{text-align:center}
.preview{margin-top:18px;padding:16px 18px;border-radius:18px;background:#fbfaff;border:1px solid var(--line);line-height:1.8;color:var(--navy)}
footer{text-align:center;padding:34px 20px;border-top:1px solid var(--line);color:var(--purple)}
footer span{display:block;color:var(--muted)}

/* difficulty */
.difficulty-panel{
  max-width:820px;margin:0 auto 18px;padding:12px 16px;border-radius:22px;background:white;border:1px solid var(--line);
  box-shadow:0 10px 28px rgba(27,22,73,.06);
  display:flex;align-items:center;justify-content:center;gap:10px;flex-wrap:wrap
}
.difficulty-panel span{font-weight:800;color:var(--navy);margin-right:4px}
.difficulty{background:#f1edf9;color:var(--purple);padding:9px 18px}
.difficulty.active{background:var(--purple);color:#fff;box-shadow:0 8px 18px rgba(71,48,154,.22)}
.level-info{
  margin:-2px 0 20px;padding:12px 16px;border-radius:16px;background:#f7f4ff;color:var(--purple);font-weight:800;text-align:center
}

/* game 24 */
.token-layout{
  display:grid;
  grid-template-columns:1.1fr .9fr .65fr;
  gap:22px;
  align-items:start;
}
.builder-col{padding:8px 0 0}
.token-bank{
  display:flex;
  flex-wrap:wrap;
  gap:12px;
  min-height:66px;
}
.token{
  border:2px solid #e3ddf3;
  color:var(--navy);
  font-weight:900;
  background:#fff;
  cursor:grab;
  user-select:none;
  transition:.15s;
}
.token:hover:not(.used), .token.selected{
  transform:translateY(-2px);
  box-shadow:0 10px 20px rgba(38,28,99,.12);
}
.token.used{opacity:.33;cursor:not-allowed}
.num-token{
  width:70px;height:70px;border-radius:22px;
  display:grid;place-items:center;
  background:linear-gradient(#fffdf6,#ffefc8);
  border-color:#f1d58e;
  font-size:34px;
}
.op-token,.paren-token{
  width:52px;height:52px;border-radius:15px;
  display:grid;place-items:center;
  background:#f8f4ff;
  border-color:#ddd1fb;
  font-size:26px;
}
.paren-token{background:#fff7ed;border-color:#f5d3a1}
.paren-col.hidden{display:none}
.workspace-wrap{margin-top:24px}
.workspace24{
  max-width:900px;
  margin:0 auto;
  display:grid;
  grid-template-columns:repeat(13, minmax(52px, 1fr));
  gap:10px;
}
.cell24{
  min-height:66px;
  border-radius:16px;
  border:2px dashed #d8d0f2;
  background:#fbfaff;
  display:grid;
  place-items:center;
  transition:.15s;
  color:#b0aacd;
  font-size:12px;
  font-weight:800;
}
.cell24.filled{
  border-style:solid;
  background:#fff;
  color:var(--navy);
  font-size:30px;
  font-weight:900;
  cursor:pointer;
}
.cell24.operator-cell{background:#faf7ff}
.cell24.number-cell{background:#fffdfa}
.cell24.paren-cell{background:#fffaf3}
.note{text-align:center;color:var(--muted)}

@media(max-width:860px){
  .topbar{padding:0 18px}
  nav{display:none}
  .brand-logo{width:48px;height:48px}
  .cards,.game-grid,.token-layout{grid-template-columns:1fr}
  .workspace24{grid-template-columns:repeat(5, minmax(52px, 1fr))}
  .cell24{min-height:58px}
  .num-token{width:64px;height:64px;font-size:30px}
  .op-token,.paren-token{width:50px;height:50px;font-size:24px}
}