:root { --bg:#07101a; --fg:#e6f7ff; --muted:#9fb7c9; --card:#0b1620; --accent:#00e5ff; --accent-2:#00ff9d; --ok:#39ffb0; --bad:#ff6b6b; --border:rgba(0,229,255,0.12); --glow:0 6px 24px rgba(0,229,255,0.08); }
html[data-theme="dark"]{ --bg:#07101a; --fg:#e6f7ff; --muted:#9fb7c9; --card:#061019; --accent:#00e5ff; --accent-2:#00ff9d; --ok:#39ffb0; --bad:#ff6b6b; --border:rgba(0,229,255,0.12); --glow:0 8px 30px rgba(0,229,255,0.12); }
*{box-sizing:border-box}
html,body{height:100%}
body{margin:0;background:var(--bg);color:var(--fg);font-family:"Noto Sans", system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;line-height:1.5; font-size:16px; line-height:1.6; -webkit-font-smoothing:antialiased; -moz-osx-font-smoothing:grayscale; }
#app{max-width:1100px;margin:0 auto;padding:16px 20px}

/* increase header vertical size to provide more length for sidebar alignment */
header{
  display:flex;
  gap:12px;
  align-items:center;
  justify-content:space-between;
  position:sticky;
  top:0;
  background:linear-gradient(180deg, rgba(0,0,0,0.25), transparent);
  padding:18px 0; /* increase vertical padding to lengthen header */
  min-height:72px; /* taller header to allow vertical alignment of controls */
  z-index:10;
  border-bottom:1px solid var(--border);
  backdrop-filter:blur(6px) saturate(130%);
  box-shadow:var(--glow);
}
.header{padding:14px 12px;} /* slightly larger inner padding for balance */
.header > .row { width: 100%; align-items: center; gap: 12px; }

/* make the primary nav take available space so controls can align on the same bar */
.header .nav{flex:1 1 auto; min-width:0; gap:8px; align-items:center;} /* ensure vertical centering */

/* ensure right-side controls stay compact */
.header .row > .row{flex:0 0 auto;}

/* increase badge and button padding slightly to fit the taller bar */
.btn{padding:12px 18px;border-radius:12px;line-height:1} /* larger padding for visual balance */
.badge{padding:8px 14px;font-size:13px;line-height:1}

/* responsive: keep behavior on small screens */
@media (max-width: 800px){
  header .nav{flex:1 1 100%; min-width:0; gap:8px;}
  header{padding:18px;}
}
.nav{display:flex;gap:8px;flex-wrap:wrap;align-items:center}
.btn{appearance:none;border:1px solid rgba(255,255,255,0.04);background:linear-gradient(180deg, rgba(255,255,255,0.02), transparent);color:var(--fg);padding:12px 18px;border-radius:12px;cursor:pointer;transition:box-shadow .12s, border-color .12s}
.btn:hover{transform:none;box-shadow:0 8px 28px rgba(0,229,255,0.06)} /* remove vertical rise so alignment stays stable */
.btn:focus-visible{box-shadow:0 0 0 6px rgba(0,229,255,0.08)}
.btn.primary{background:linear-gradient(90deg, rgba(0,229,255,0.08), rgba(0,255,157,0.06));border-color:var(--accent);color:var(--bg);box-shadow:0 6px 20px rgba(0,229,255,0.12), 0 0 18px rgba(0,255,157,0.04);backdrop-filter:blur(4px)}
.btn.ghost{background:transparent}
.btn.active{background:var(--accent);color:#fff;border-color:var(--accent)}
.badge{display:inline-block;padding:4px 10px;border:1px solid var(--border);border-radius:999px;font-size:12px;color:var(--muted);background:var(--bg)}
.card{border:1px solid rgba(255,255,255,0.03);background:linear-gradient(180deg, rgba(255,255,255,0.012), rgba(0,0,0,0.04));border-radius:14px;padding:20px;box-shadow:var(--glow)}
.grid{display:grid;gap:16px}
.grid.cols-2{grid-template-columns:repeat(2,minmax(0,1fr))}
@media (max-width: 800px){ .grid.cols-2{grid-template-columns:1fr} }
h1,h2,h3{margin:8px 0 6px}
h1{font-size:26px} h2{font-size:20px} h3{font-size:16px}
small{color:var(--muted)}
.progress{height:10px;background:var(--border);border-radius:999px;overflow:hidden}
.progress > span{display:block;height:100%;background:var(--accent);width:0%;transition:width .35s ease}
.list{display:flex;flex-direction:column;gap:10px}
.row{display:flex;align-items:center;justify-content:space-between;gap:10px}
.code{background:linear-gradient(90deg, rgba(0,0,0,0.18), rgba(0,0,0,0.08));border:1px solid rgba(255,255,255,0.02);padding:14px;border-radius:12px; font-family: "Space Mono", ui-monospace, SFMono-Regular, Menlo, Monaco, "Roboto Mono", monospace; font-size:13px; line-height:1.5; }
.kbd{font-family:inherit;border:1px solid var(--border);padding:2px 6px;border-radius:6px;background:var(--bg)}
.input, select{width:100%;padding:10px;border:1px solid(var(--border));background:var(--bg);color:var(--fg);border-radius:10px;transition:border-color .2s, box-shadow .2s; font-size:15px; }
.input:focus, select:focus{outline:none;border-color:color-mix(in oklab, var(--accent) 60%, var(--border));box-shadow:0 0 0 3px color-mix(in oklab, var(--accent) 25%, transparent)}
.choice{border:1px solid rgba(255,255,255,0.04);background:linear-gradient(180deg, rgba(255,255,255,0.01), transparent);transition:box-shadow .12s, transform .08s}
.choice:hover{background:color-mix(in oklab, var(--bg) 92%, var(--card))}
.choice.selected{outline:none;box-shadow:0 8px 30px rgba(0,229,255,0.10);transform:translateY(-2px)}
.choice.correct{box-shadow:0 8px 30px rgba(57,255,176,0.10);border-color:var(--ok)}
.choice.wrong{box-shadow:0 8px 24px rgba(255,107,107,0.08);border-color:var(--bad)}
.footer-actions{display:flex;gap:8px;justify-content:flex-end;margin-top:12px}
#toast{position:fixed;bottom:22px;left:50%;transform:translateX(-50%);background:linear-gradient(90deg, rgba(0,229,255,0.08), rgba(0,255,157,0.04));color:var(--fg);padding:10px 16px;border-radius:999px;opacity:0;pointer-events:none;transition:opacity .18s, transform .18s;backdrop-filter:blur(6px)}
#toast.show{opacity:1;transform:translateX(-50%) translateY(-6px)}