:root {
  --bg: #0f1220;
  --bg2: #161a2e;
  --card: #1c2140;
  --card2: #232a50;
  --line: #2e3766;
  --txt: #e7e9f5;
  --mute: #9aa3c7;
  --acc: #7c8cff;
  --acc2: #4fd1c5;
  --ok: #3ddc97;
  --ko: #ff6b81;
  --warn: #ffc857;
  --code-bg: #12152a;
  --radius: 14px;
}
* { box-sizing: border-box; }
html, body { margin: 0; height: 100%; }
body {
  font-family: "Segoe UI", system-ui, -apple-system, sans-serif;
  background: var(--bg); color: var(--txt);
  display: flex; font-size: 16px; line-height: 1.55;
}
a { color: var(--acc2); }
code, pre, textarea, .mono { font-family: "Cascadia Code", "Consolas", "Fira Code", monospace; }

/* ---------- Sidebar ---------- */
#side {
  width: 290px; min-width: 290px; height: 100vh; overflow-y: auto;
  background: var(--bg2); border-right: 1px solid var(--line);
  padding: 18px 14px; position: sticky; top: 0;
}
#side h1 { font-size: 19px; margin: 0 0 4px; }
#side .sub { color: var(--mute); font-size: 13px; margin-bottom: 14px; }
.progress { background: var(--card); border-radius: 99px; height: 10px; overflow: hidden; }
.progress > div { height: 100%; background: linear-gradient(90deg, var(--acc), var(--acc2)); transition: width .4s; }
.prog-label { font-size: 13px; color: var(--mute); margin: 6px 0 16px; display: flex; justify-content: space-between; }
.nav-group { font-size: 12px; text-transform: uppercase; letter-spacing: .08em; color: var(--mute); margin: 18px 6px 6px; }
.nav-item {
  display: flex; align-items: center; gap: 8px; padding: 8px 10px; border-radius: 10px;
  cursor: pointer; color: var(--txt); font-size: 14.5px; user-select: none;
}
.nav-item:hover { background: var(--card); }
.nav-item.active { background: var(--card2); box-shadow: inset 3px 0 0 var(--acc); }
.nav-item .badge { margin-left: auto; font-size: 12px; color: var(--mute); }
.nav-item .badge.full { color: var(--ok); }

/* ---------- Main ---------- */
#main { flex: 1; height: 100vh; overflow-y: auto; scroll-behavior: smooth; }
#content { max-width: 920px; margin: 0 auto; padding: 32px 28px 120px; }
h2.page-title { font-size: 30px; margin: 0 0 6px; }
.page-sub { color: var(--mute); margin-bottom: 26px; }
h3 { margin: 30px 0 10px; font-size: 21px; }
.card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 18px 20px; margin: 18px 0;
}
.card h4 { margin: 0 0 10px; font-size: 17px; display: flex; align-items: center; gap: 8px; }
.card h4 .tag { font-size: 11px; padding: 2px 8px; border-radius: 99px; background: var(--card2); color: var(--mute); font-weight: 500; }
.card.done { border-color: rgba(61,220,151,.45); }
.card.done h4::after { content: "✔"; color: var(--ok); margin-left: auto; }

.callout { border-radius: 12px; padding: 12px 16px; margin: 16px 0; border-left: 4px solid; background: var(--card); }
.callout.key { border-color: var(--acc); }
.callout.tip { border-color: var(--acc2); }
.callout.warn { border-color: var(--warn); background: rgba(255,200,87,.07); }
.callout.danger { border-color: var(--ko); background: rgba(255,107,129,.07); }
.callout b.t { display: block; margin-bottom: 4px; }

/* ---------- Code ---------- */
pre.code {
  background: var(--code-bg); border: 1px solid var(--line); border-radius: 10px;
  padding: 12px 14px; overflow-x: auto; font-size: 14.5px; margin: 10px 0; line-height: 1.5;
}
code.inl { background: var(--code-bg); padding: 1px 6px; border-radius: 6px; font-size: .92em; color: #ffd38a; }
.kw { color: #c792ea; } .str { color: #c3e88d; } .num { color: #f78c6c; }
.bi { color: #82aaff; } .com { color: #6b7499; font-style: italic; } .fn { color: #ffcb6b; }

/* ---------- Buttons / inputs ---------- */
button {
  font: inherit; font-size: 14px; border: 1px solid var(--line); background: var(--card2); color: var(--txt);
  padding: 8px 14px; border-radius: 10px; cursor: pointer; transition: .15s;
}
button:hover { border-color: var(--acc); }
button.primary { background: var(--acc); border-color: var(--acc); color: #0b0e1d; font-weight: 600; }
button.primary:hover { filter: brightness(1.1); }
button.ghost { background: transparent; }
button:disabled { opacity: .5; cursor: default; }
.row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin-top: 12px; }
input[type=text], textarea.ans, select {
  font: inherit; background: var(--code-bg); color: var(--txt); border: 1px solid var(--line);
  border-radius: 10px; padding: 9px 12px; width: 100%; font-family: "Cascadia Code", Consolas, monospace; font-size: 14.5px;
}
textarea.ans { min-height: 80px; resize: vertical; }
select { width: auto; font-family: inherit; }
input:focus, textarea:focus, select:focus { outline: none; border-color: var(--acc); }
label.field { display: block; font-size: 13.5px; color: var(--mute); margin: 12px 0 5px; }

.fb { margin-top: 12px; padding: 10px 14px; border-radius: 10px; font-size: 14.5px; display: none; }
.fb.show { display: block; }
.fb.ok { background: rgba(61,220,151,.1); border: 1px solid rgba(61,220,151,.4); }
.fb.ko { background: rgba(255,107,129,.1); border: 1px solid rgba(255,107,129,.4); }
.fb.info { background: rgba(124,140,255,.1); border: 1px solid rgba(124,140,255,.4); }
.reveal { display: none; margin-top: 12px; border-top: 1px dashed var(--line); padding-top: 12px; }
.reveal.show { display: block; animation: fade .3s; }
@keyframes fade { from { opacity: 0; transform: translateY(-4px);} to {opacity: 1;} }

/* ---------- QCM ---------- */
.opts { display: grid; gap: 8px; margin-top: 10px; }
.opt {
  padding: 10px 14px; border: 1px solid var(--line); border-radius: 10px; cursor: pointer; background: var(--code-bg);
  font-family: "Cascadia Code", Consolas, monospace; font-size: 14.5px;
}
.opt:hover { border-color: var(--acc); }
.opt.good { border-color: var(--ok); background: rgba(61,220,151,.12); }
.opt.bad { border-color: var(--ko); background: rgba(255,107,129,.12); }
.opt.locked { pointer-events: none; }

/* ---------- Editor ---------- */
.editor-wrap { position: relative; margin-top: 10px; }
textarea.editor {
  width: 100%; min-height: 200px; background: var(--code-bg); color: var(--txt);
  border: 1px solid var(--line); border-radius: 10px; padding: 12px 14px; font-size: 14.5px; line-height: 1.5;
  resize: vertical; tab-size: 4; white-space: pre; overflow-x: auto;
}
textarea.editor:focus { outline: none; border-color: var(--acc); }
.console {
  background: #0a0c18; border: 1px solid var(--line); border-radius: 10px; padding: 10px 14px; margin-top: 10px;
  font-family: "Cascadia Code", Consolas, monospace; font-size: 13.5px; white-space: pre-wrap; display: none; max-height: 340px; overflow: auto;
}
.console.show { display: block; }
.t-ok { color: var(--ok); } .t-ko { color: var(--ko); } .t-mute { color: var(--mute); } .t-warn { color: var(--warn); }

/* ---------- Tracer ---------- */
.tracer { display: grid; grid-template-columns: minmax(0, 1.1fr) minmax(0, 1fr); gap: 14px; margin-top: 10px; }
@media (max-width: 900px) { .tracer { grid-template-columns: 1fr; } #side { display: none; } }
.tr-code { background: var(--code-bg); border: 1px solid var(--line); border-radius: 10px; padding: 8px 0; font-size: 14px; overflow-x: auto; }
.tr-line { display: flex; white-space: pre; padding: 0 10px 0 0; min-height: 21px; }
.tr-line .ln { width: 38px; text-align: right; padding-right: 10px; color: #4b557f; user-select: none; flex-shrink: 0; }
.tr-line.cur { background: rgba(124,140,255,.22); box-shadow: inset 3px 0 0 var(--acc); }
.tr-line.prev { background: rgba(79,209,197,.08); }
.tr-side { display: flex; flex-direction: column; gap: 10px; min-width: 0; }
.tr-panel { background: var(--code-bg); border: 1px solid var(--line); border-radius: 10px; padding: 8px 12px; font-size: 13.5px; }
.tr-panel .ttl { font-size: 11.5px; text-transform: uppercase; letter-spacing: .08em; color: var(--mute); margin-bottom: 6px; }
.frame { border: 1px solid var(--line); border-radius: 8px; padding: 6px 10px; margin-top: 6px; background: var(--bg2); }
.frame.top { border-color: var(--acc); }
.frame .fname { font-size: 12.5px; color: var(--acc); font-weight: 600; margin-bottom: 4px; }
.var { display: flex; gap: 8px; align-items: flex-start; font-family: "Cascadia Code", Consolas, monospace; padding: 2px 0; flex-wrap: wrap; }
.var .vn { color: #ffcb6b; min-width: 54px; }
.var.changed { animation: flash 1s; border-radius: 4px; }
@keyframes flash { from { background: rgba(255,200,87,.35);} to { background: transparent; } }
.obj { display: inline-flex; align-items: center; gap: 4px; flex-wrap: wrap; }
.oid { font-size: 10.5px; padding: 0 6px; border-radius: 99px; color: #0b0e1d; font-weight: 700; font-family: "Segoe UI", sans-serif; }
.dictbox { display: inline-block; border-left: 2px solid var(--line); padding-left: 8px; }
.tr-out { white-space: pre-wrap; font-family: "Cascadia Code", Consolas, monospace; min-height: 22px; color: #d7f5e9; }
.tr-ret { color: var(--ok); font-family: "Cascadia Code", Consolas, monospace; }
.tr-controls { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; margin-top: 10px; }
.tr-controls input[type=range] { flex: 1; min-width: 120px; accent-color: var(--acc); }
.tr-note { margin-top: 10px; padding: 10px 14px; border-radius: 10px; background: rgba(124,140,255,.1); border: 1px solid rgba(124,140,255,.3); font-size: 14.5px; min-height: 44px; }
.tr-step { font-size: 13px; color: var(--mute); min-width: 92px; text-align: center; }

/* ---------- Home ---------- */
.grid2 { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
@media (max-width: 760px) { .grid2 { grid-template-columns: 1fr; } }
.tile { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); padding: 18px; cursor: pointer; transition: .15s; }
.tile:hover { border-color: var(--acc); transform: translateY(-2px); }
.tile .big { font-size: 28px; }
.tile h4 { margin: 6px 0; }
.tile p { color: var(--mute); margin: 0; font-size: 14.5px; }
.nextbar { display: flex; justify-content: space-between; margin-top: 40px; gap: 10px; }

table.t { border-collapse: collapse; width: 100%; font-size: 14.5px; margin: 10px 0; }
table.t th, table.t td { border: 1px solid var(--line); padding: 7px 10px; text-align: left; vertical-align: top; }
table.t th { background: var(--card2); }

/* ---------- Timer ---------- */
#timer {
  position: fixed; right: 18px; top: 14px; background: var(--card2); border: 1px solid var(--acc);
  border-radius: 12px; padding: 8px 14px; font-weight: 700; font-size: 18px; display: none; z-index: 10; gap: 10px; align-items: center;
}
#timer.show { display: flex; }
#timer button { padding: 3px 9px; font-size: 12px; }