/* Advanced Topics – shared stylesheet */
:root {
  --bg-start:#0a4d2e;--bg-mid:#1a7f4f;--bg-end:#2ea86f;
  --accent:#4dd994;--accent2:#ffd700;--text:#fff;--muted:#e8fff0;
  --radius:16px;--card-bg:linear-gradient(135deg,#0d5a38 0%,#0a4d2e 100%);
}
*,*::before,*::after{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,sans-serif;
  background:linear-gradient(160deg,var(--bg-start) 0%,var(--bg-mid) 50%,var(--bg-end) 100%) fixed;
  color:var(--text);min-height:100vh;line-height:1.6;
}

/* ── Nav ── */
.top-nav{
  position:sticky;top:0;z-index:100;
  background:linear-gradient(90deg,rgba(10,77,46,.95),rgba(26,127,79,.95));
  backdrop-filter:blur(10px);border-bottom:1px solid rgba(77,217,148,.3);
  padding:10px 24px;display:flex;align-items:center;gap:12px;flex-wrap:wrap;
}
.nav-back{
  display:inline-flex;align-items:center;gap:6px;
  background:rgba(77,217,148,.2);border:1px solid rgba(77,217,148,.5);
  color:var(--accent);padding:7px 16px;border-radius:999px;
  text-decoration:none;font-size:13px;font-weight:600;
  transition:all .2s ease;
}
.nav-back:hover{background:rgba(77,217,148,.35);transform:translateX(-2px)}
.nav-title{font-size:15px;font-weight:700;color:#fff;margin-left:4px}

/* ── Header ── */
.topic-header{
  max-width:900px;margin:36px auto 0;padding:0 24px;
}
.topic-badge{
  display:inline-block;padding:5px 14px;border-radius:999px;
  font-size:12px;font-weight:700;letter-spacing:.5px;
  background:linear-gradient(135deg,rgba(77,217,148,.9),rgba(63,196,129,.9));
  color:#0a4d2e;margin-bottom:14px;
}
.topic-header h1{
  font-size:clamp(26px,5vw,44px);font-weight:800;
  text-shadow:0 2px 10px rgba(0,0,0,.5);margin-bottom:10px;
}
.topic-header .subtitle{color:var(--muted);font-size:clamp(14px,2vw,17px);opacity:.9}

/* ── Tab bar ── */
.tabs-wrap{max-width:900px;margin:28px auto 0;padding:0 24px}
.tab-bar{
  display:flex;flex-wrap:wrap;gap:6px;
  background:rgba(0,0,0,.25);padding:8px;border-radius:var(--radius);
  border:1px solid rgba(77,217,148,.2);margin-bottom:24px;
}
.tab-btn{
  flex:1 1 auto;min-width:120px;padding:9px 12px;border:none;cursor:pointer;
  border-radius:10px;font-size:12.5px;font-weight:600;
  background:transparent;color:rgba(255,255,255,.65);
  transition:all .25s ease;white-space:nowrap;text-align:center;
}
.tab-btn:hover{background:rgba(77,217,148,.15);color:#fff}
.tab-btn.active{
  background:linear-gradient(135deg,var(--accent),#3fc481);
  color:#0a4d2e;box-shadow:0 4px 12px rgba(77,217,148,.35);
}

/* ── Section panels ── */
.tab-panel{display:none}
.tab-panel.active{display:block}
.section-card{
  background:var(--card-bg);border:1px solid rgba(77,217,148,.25);
  border-radius:var(--radius);padding:28px;margin-bottom:20px;
}
.section-card h2{
  color:var(--accent);font-size:1.25rem;font-weight:700;
  margin-bottom:16px;padding-bottom:10px;
  border-bottom:1px solid rgba(77,217,148,.2);
}
.section-card h3{color:#b8ffe0;font-size:1rem;font-weight:600;margin:16px 0 8px}
.section-card p{color:var(--muted);margin-bottom:12px}
.section-card ul,.section-card ol{color:var(--muted);padding-left:22px;margin-bottom:12px}
.section-card li{margin-bottom:6px}
.section-card strong{color:#fff}
.section-card a{color:var(--accent);text-decoration:none}
.section-card a:hover{text-decoration:underline}

/* ── Hand diagrams ── */
.hand-grid{
  display:grid;grid-template-columns:1fr 1fr;gap:16px;margin:16px 0;
}
@media(max-width:560px){.hand-grid{grid-template-columns:1fr}}
.hand-card{
  background:rgba(0,0,0,.3);border:1px solid rgba(255,255,255,.1);
  border-radius:12px;padding:16px;font-family:"Courier New",monospace;
  font-size:14px;
}
.hand-card .hand-label{
  font-family:system-ui;font-weight:700;color:var(--accent);
  margin-bottom:10px;font-size:13px;
}
.suit-row{margin:3px 0;color:#e8fff0}
.suit-row .spades{color:#a8c8ff}
.suit-row .hearts{color:#ff8888}
.suit-row .diamonds{color:#ffcc44}
.suit-row .clubs{color:#88dd88}
.hcp{font-size:11px;color:rgba(255,255,255,.5);margin-top:6px}

/* ── Bidding tables ── */
.bid-table{width:100%;border-collapse:collapse;margin:14px 0;font-size:14px}
.bid-table th{
  background:rgba(77,217,148,.2);color:var(--accent);
  padding:8px 12px;text-align:left;border-bottom:1px solid rgba(77,217,148,.3);
  font-weight:600;font-size:13px;
}
.bid-table td{
  padding:8px 12px;border-bottom:1px solid rgba(255,255,255,.06);
  color:var(--muted);
}
.bid-table tr:hover td{background:rgba(255,255,255,.04)}
.bid{font-weight:700;color:#fff;font-family:"Courier New",monospace}

/* ── Decision tree ── */
.dtree{margin:16px 0}
.dt-node{
  background:rgba(0,0,0,.3);border:1px solid rgba(77,217,148,.3);
  border-radius:10px;padding:12px 16px;margin:8px 0;
  cursor:pointer;transition:all .2s ease;
  display:flex;justify-content:space-between;align-items:flex-start;gap:12px;
}
.dt-node:hover{background:rgba(77,217,148,.1);border-color:rgba(77,217,148,.6)}
.dt-node .dt-q{color:#fff;font-weight:600;font-size:14px;flex:1}
.dt-node .dt-arrow{color:var(--accent);font-size:18px;flex-shrink:0;transition:transform .2s}
.dt-node.open .dt-arrow{transform:rotate(90deg)}
.dt-children{
  display:none;padding-left:20px;border-left:2px solid rgba(77,217,148,.3);
  margin-left:12px;margin-top:4px;
}
.dt-children.open{display:block}
.dt-leaf{
  background:rgba(77,217,148,.08);border:1px solid rgba(77,217,148,.2);
  border-radius:8px;padding:10px 14px;margin:6px 0;color:var(--muted);font-size:14px;
}
.dt-leaf .dt-bid{color:var(--accent);font-weight:700;font-family:"Courier New",monospace}

/* ── Quizzes ── */
.quiz-item{
  background:rgba(0,0,0,.25);border:1px solid rgba(255,255,255,.1);
  border-radius:12px;padding:20px;margin-bottom:16px;
}
.quiz-q{color:#fff;font-weight:600;margin-bottom:14px;font-size:15px}
.quiz-hand{
  font-family:"Courier New",monospace;font-size:13px;
  background:rgba(0,0,0,.3);border-radius:8px;padding:12px;
  margin-bottom:14px;line-height:2;
}
.quiz-options{display:flex;flex-direction:column;gap:8px;margin-bottom:12px}
.quiz-opt{
  background:rgba(255,255,255,.07);border:1px solid rgba(255,255,255,.15);
  border-radius:8px;padding:10px 14px;cursor:pointer;
  color:var(--muted);font-size:14px;text-align:left;
  transition:all .2s ease;
}
.quiz-opt:hover:not([disabled]){background:rgba(77,217,148,.15);border-color:rgba(77,217,148,.5);color:#fff}
.quiz-opt.correct{background:rgba(77,217,148,.25);border-color:#4dd994;color:#fff}
.quiz-opt.wrong{background:rgba(220,50,50,.2);border-color:#e05050;color:#ffaaaa}
.quiz-opt.reveal{background:rgba(77,217,148,.15);border-color:rgba(77,217,148,.4)}
.quiz-explanation{
  display:none;background:rgba(77,217,148,.08);
  border-left:3px solid var(--accent);border-radius:4px;
  padding:12px 16px;font-size:14px;color:var(--muted);margin-top:8px;
}
.quiz-explanation.show{display:block}
.quiz-score{
  background:rgba(77,217,148,.15);border:1px solid rgba(77,217,148,.4);
  border-radius:10px;padding:14px;text-align:center;font-weight:600;
  color:#fff;margin-top:12px;display:none;
}

/* ── Practice sequences ── */
.seq-block{
  background:rgba(0,0,0,.25);border:1px solid rgba(255,255,255,.1);
  border-radius:12px;padding:20px;margin-bottom:16px;
}
.seq-title{color:#b8ffe0;font-weight:700;margin-bottom:10px}
.seq-table{width:100%;border-collapse:collapse;font-family:"Courier New",monospace;font-size:14px}
.seq-table th{color:rgba(255,255,255,.5);font-size:12px;padding:4px 8px;text-align:center;letter-spacing:.5px}
.seq-table td{padding:6px 8px;text-align:center;color:#fff}
.seq-table td.note{font-family:system-ui;font-size:12px;color:var(--muted);text-align:left;padding-left:16px}
.seq-table tr:nth-child(even) td{background:rgba(255,255,255,.04)}

/* ── Convention card box ── */
.cc-box{
  background:rgba(0,0,0,.3);border:2px solid rgba(255,215,0,.4);
  border-radius:12px;padding:20px;margin:12px 0;
}
.cc-box h3{color:#ffd700;margin-bottom:12px}
.cc-row{display:flex;gap:12px;flex-wrap:wrap;margin-bottom:8px;align-items:flex-start}
.cc-label{color:rgba(255,255,255,.5);font-size:13px;min-width:160px;flex-shrink:0}
.cc-val{color:var(--muted);font-size:13px;flex:1}

/* ── Expert mistakes ── */
.mistake-item{
  background:rgba(220,50,50,.1);border:1px solid rgba(220,50,50,.3);
  border-radius:12px;padding:18px;margin-bottom:14px;
}
.mistake-item h3{color:#ff9090;margin-bottom:8px;font-size:15px}
.mistake-item p{color:var(--muted);font-size:14px;margin-bottom:6px}
.mistake-fix{
  background:rgba(77,217,148,.1);border-left:3px solid var(--accent);
  padding:10px 14px;border-radius:4px;font-size:14px;color:var(--muted);margin-top:8px;
}
.mistake-fix strong{color:var(--accent)}

/* ── Misunderstandings ── */
.misunderstanding{
  background:rgba(255,150,0,.08);border:1px solid rgba(255,150,0,.3);
  border-radius:12px;padding:18px;margin-bottom:14px;
}
.misunderstanding h3{color:#ffaa44;margin-bottom:8px;font-size:15px}
.misunderstanding p{color:var(--muted);font-size:14px;margin-bottom:6px}

/* ── Suit symbol colours ── */
.suit-s { color: #a8c8ff; }   /* ♠ spades  – soft blue   */
.suit-h { color: #ff6b6b; }   /* ♥ hearts  – red         */
.suit-d { color: #ffaa44; }   /* ♦ diamonds – orange     */
.suit-c { color: #66dd88; }   /* ♣ clubs   – green       */

/* ── Utility ── */
.badge-pill{
  display:inline-block;padding:3px 10px;border-radius:999px;
  font-size:11px;font-weight:700;margin-right:6px;
}
.badge-gf{background:rgba(77,217,148,.2);color:#4dd994;border:1px solid rgba(77,217,148,.4)}
.badge-inv{background:rgba(255,200,0,.2);color:#ffd700;border:1px solid rgba(255,200,0,.4)}
.badge-sig{background:rgba(100,150,255,.2);color:#88aaff;border:1px solid rgba(100,150,255,.4)}
.alert-box{
  background:rgba(255,200,0,.1);border:1px solid rgba(255,200,0,.4);
  border-radius:10px;padding:14px 18px;margin:12px 0;color:var(--muted);font-size:14px;
}
.alert-box strong{color:#ffd700}
.tip-box{
  background:rgba(77,217,148,.08);border:1px solid rgba(77,217,148,.3);
  border-radius:10px;padding:14px 18px;margin:12px 0;color:var(--muted);font-size:14px;
}
.tip-box strong{color:var(--accent)}
hr.sep{border:none;border-top:1px solid rgba(255,255,255,.08);margin:20px 0}

/* ── Footer ── */
footer{text-align:center;padding:28px;color:rgba(255,255,255,.4);font-size:13px}
footer a{color:var(--accent);text-decoration:none}

@media(max-width:640px){
  .tab-btn{min-width:90px;font-size:11px;padding:8px 8px}
  .section-card{padding:18px}
  .topic-header{margin-top:20px}
}