:root {
  --bg: #f1f5f9;
  --card: #ffffff;
  --ink: #0f172a;
  --muted: #64748b;
  --line: #e2e8f0;
  --brand: #2563eb;
  --brand-ink: #1d4ed8;
  --ok: #15803d;
  --ok-bg: #dcfce7;
  --bug: #b91c1c;
  --bug-bg: #fee2e2;
  --shadow: 0 1px 3px rgba(15, 23, 42, .08), 0 8px 24px rgba(15, 23, 42, .05);
  --radius: 14px;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.55;
}

.wrap {
  width: min(920px, 92vw);
  margin-inline: auto;
}

/* Header */
.site-header {
  background: linear-gradient(135deg, #1e3a8a, #2563eb);
  color: #fff;
  padding: 2.2rem 0 2.4rem;
}
.site-header h1 {
  margin: 0;
  font-size: clamp(1.6rem, 3vw, 2.3rem);
  font-weight: 750;
  letter-spacing: -.02em;
}
.site-header .tag {
  display: inline-block;
  vertical-align: middle;
  margin-left: .5rem;
  padding: .18em .6em;
  font-size: .5em;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .08em;
  background: rgba(255, 255, 255, .18);
  border-radius: 999px;
}
.subtitle { margin: .4rem 0 0; opacity: .9; }

/* Cards */
main { padding: 1.6rem 0 3rem; }
.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.3rem 1.4rem;
  margin-bottom: 1.2rem;
}
.card h2 {
  margin: 0 0 .9rem;
  font-size: 1.15rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

/* Intro */
.intro-head { display: flex; align-items: center; justify-content: space-between; }
.intro-head h2 { margin: 0; }
.intro-body p { margin: .6rem 0; }
.notes { margin: .6rem 0 0; padding-left: 1.2rem; color: var(--muted); }
.notes li { margin: .25rem 0; }
.intro.collapsed .intro-body { display: none; }

code {
  background: #f1f5f9;
  border: 1px solid var(--line);
  border-radius: 6px;
  padding: .05em .4em;
  font-size: .9em;
}

/* Form */
.sides {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
}
.sides label {
  display: flex;
  flex-direction: column;
  gap: .35rem;
  font-weight: 600;
  font-size: .95rem;
}
.sides input {
  font-size: 1.25rem;
  padding: .6rem .7rem;
  border: 1.5px solid var(--line);
  border-radius: 10px;
  background: #fff;
  transition: border-color .15s, box-shadow .15s;
}
.sides input:focus {
  outline: none;
  border-color: var(--brand);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, .15);
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: .7rem;
  margin-top: 1.1rem;
}
.btn {
  font: inherit;
  font-weight: 600;
  padding: .6rem 1.1rem;
  border-radius: 10px;
  border: 1.5px solid var(--line);
  background: #fff;
  color: var(--ink);
  cursor: pointer;
  transition: background .15s, border-color .15s, transform .05s;
}
.btn:hover { background: #f8fafc; }
.btn:active { transform: translateY(1px); }
.btn.primary { background: var(--brand); border-color: var(--brand); color: #fff; }
.btn.primary:hover { background: var(--brand-ink); }
.btn.danger { color: var(--bug); border-color: #fecaca; }
.btn.danger:hover { background: var(--bug-bg); }
.link-btn {
  background: none; border: none; color: var(--brand);
  font: inherit; font-weight: 600; cursor: pointer; padding: 0;
}

/* Result */
.result {
  margin-top: 1.2rem;
  padding: 1rem 1.1rem;
  border-radius: 12px;
  background: #f8fafc;
  border: 1px solid var(--line);
}
.verdict { display: flex; align-items: baseline; gap: .6rem; flex-wrap: wrap; }
.verdict-label { color: var(--muted); font-weight: 600; }
.verdict-value { font-size: 1.35rem; font-weight: 750; }
.feedback { margin: .6rem 0 0; font-weight: 600; }
.feedback.bug { color: var(--bug); }
.feedback.ok { color: var(--ok); }
.feedback.neutral { color: var(--muted); font-weight: 500; }

/* Trackers */
.trackers {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.2rem;
}
.counter {
  font-size: .95rem;
  font-weight: 700;
  color: #fff;
  background: var(--brand);
  border-radius: 999px;
  padding: .12em .7em;
}
.slots { list-style: none; margin: 0; padding: 0; counter-reset: slot; }
.slots li {
  display: flex;
  align-items: flex-start;
  gap: .6rem;
  padding: .55rem .2rem;
  border-top: 1px solid var(--line);
  color: var(--muted);
}
.slots li:first-child { border-top: none; }
.slots li .mark {
  flex: none;
  width: 1.5rem; height: 1.5rem;
  border-radius: 50%;
  display: grid; place-items: center;
  font-size: .8rem; font-weight: 700;
  background: #f1f5f9; color: var(--muted);
  border: 1px solid var(--line);
}
.slots li .body { flex: 1; }
.slots li .body .concept,
.slots li .body .example {
  display: block;
  font-weight: 400;
  font-size: .85rem;
  color: var(--muted);
  margin-top: .15rem;
}
.slots li.found { color: var(--ink); font-weight: 600; }
.slots li.found .mark { background: var(--ok-bg); color: var(--ok); border-color: #bbf7d0; }
.tracker.bugs .slots li.found .mark { background: var(--bug-bg); color: var(--bug); border-color: #fecaca; }
.slots li.just-found { animation: pop .5s ease; }

@keyframes pop {
  0% { background: #fef9c3; }
  100% { background: transparent; }
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--line);
  padding: 1.4rem 0;
  color: var(--muted);
  font-size: .9rem;
}
.site-footer p { margin: 0; }

@media (max-width: 640px) {
  .sides { grid-template-columns: 1fr; }
  .trackers { grid-template-columns: 1fr; }
}