:root {
  --ink: #0e1419;
  --ink-2: #1a242d;
  --panel: rgba(22, 32, 42, 0.72);
  --line: rgba(180, 210, 230, 0.14);
  --text: #e8eef3;
  --muted: #93a4b3;
  --gcp: #5b9fff;
  --gcp-deep: #2f6fed;
  --cf: #f5a524;
  --ok: #3dd68c;
  --warn: #ff7b72;
  --radius: 14px;
  --font-display: "Bricolage Grotesque", system-ui, sans-serif;
  --font-body: "IBM Plex Sans", system-ui, sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, monospace;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  color: var(--text);
  font-family: var(--font-body);
  background:
    radial-gradient(1200px 600px at 10% -10%, rgba(47, 111, 237, 0.28), transparent 55%),
    radial-gradient(900px 500px at 90% 0%, rgba(245, 165, 36, 0.12), transparent 50%),
    linear-gradient(180deg, #0b1015 0%, var(--ink) 40%, #0a1218 100%);
  background-attachment: fixed;
}

.noise {
  pointer-events: none;
  position: fixed;
  inset: 0;
  opacity: 0.035;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
  z-index: 0;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(rgba(91, 159, 255, 0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(91, 159, 255, 0.04) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse at center, black 30%, transparent 75%);
  pointer-events: none;
  z-index: 0;
}

.top, main, .foot { position: relative; z-index: 1; }

.top {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem 1.5rem;
  align-items: flex-end;
  justify-content: space-between;
  padding: 1.5rem clamp(1rem, 3vw, 2.5rem) 1rem;
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(10px);
}

.brand {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: clamp(1.4rem, 2.5vw, 1.85rem);
  letter-spacing: -0.03em;
}
.brand-sub {
  margin: 0.2rem 0 0;
  color: var(--muted);
  font-size: 0.88rem;
}

.tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  padding: 0.25rem;
  background: rgba(0, 0, 0, 0.35);
  border: 1px solid var(--line);
  border-radius: 999px;
}
.tab {
  border: 0;
  background: transparent;
  color: var(--muted);
  font: 500 0.9rem var(--font-body);
  padding: 0.55rem 1rem;
  border-radius: 999px;
  cursor: pointer;
  transition: background 0.2s, color 0.2s, transform 0.15s;
}
.tab:hover { color: var(--text); }
.tab.is-active {
  background: linear-gradient(135deg, var(--gcp-deep), #1f4fb8);
  color: white;
  box-shadow: 0 6px 20px rgba(47, 111, 237, 0.35);
}

main {
  padding: 1.5rem clamp(1rem, 3vw, 2.5rem) 3rem;
  max-width: 1180px;
  margin: 0 auto;
}

.panel[hidden] { display: none; }
.panel.is-active { animation: rise 0.35s ease; }
@keyframes rise {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: none; }
}

.panel-head h1 {
  margin: 0 0 0.35rem;
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 3vw, 2.1rem);
  letter-spacing: -0.03em;
}
.panel-head p {
  margin: 0 0 1rem;
  color: var(--muted);
  max-width: 52ch;
}

.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 0.85rem;
}
.chip {
  border: 1px solid var(--line);
  background: rgba(255,255,255,0.03);
  color: var(--muted);
  font: 500 0.8rem var(--font-body);
  padding: 0.35rem 0.75rem;
  border-radius: 999px;
  cursor: pointer;
}
.chip.is-active {
  border-color: rgba(91, 159, 255, 0.55);
  color: var(--text);
  background: rgba(91, 159, 255, 0.12);
}

.search {
  width: min(420px, 100%);
  margin-bottom: 1.25rem;
  padding: 0.7rem 0.9rem;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: rgba(0,0,0,0.35);
  color: var(--text);
  font: 400 0.95rem var(--font-body);
}
.search:focus {
  outline: 2px solid rgba(91, 159, 255, 0.45);
  outline-offset: 1px;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 0.9rem;
}

.k-card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem 1.1rem 1.15rem;
  transition: border-color 0.2s, transform 0.2s;
}
.k-card:hover {
  border-color: rgba(91, 159, 255, 0.4);
  transform: translateY(-2px);
}
.k-card .domain {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--gcp);
  margin: 0 0 0.4rem;
}
.k-card h3 {
  margin: 0 0 0.45rem;
  font-family: var(--font-display);
  font-size: 1.15rem;
  letter-spacing: -0.02em;
}
.k-card .what { margin: 0 0 0.75rem; color: var(--muted); font-size: 0.92rem; line-height: 1.45; }
.k-card h4 {
  margin: 0.6rem 0 0.3rem;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--cf);
}
.k-card ul {
  margin: 0;
  padding-left: 1.1rem;
  color: var(--text);
  font-size: 0.88rem;
  line-height: 1.45;
}
.k-card li { margin-bottom: 0.25rem; }
.k-card .when, .k-card .trap {
  margin: 0.55rem 0 0;
  font-size: 0.85rem;
  line-height: 1.4;
  color: var(--muted);
}
.k-card .trap strong { color: var(--warn); font-weight: 600; }

.compare-list { display: flex; flex-direction: column; gap: 0.75rem; }
.compare-row {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 0.75rem;
  align-items: stretch;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1rem;
}
.compare-row .side h3 {
  margin: 0 0 0.35rem;
  font-family: var(--font-display);
  font-size: 1.05rem;
}
.compare-row .side p { margin: 0; color: var(--muted); font-size: 0.88rem; line-height: 1.4; }
.compare-row .mid {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.35rem;
  min-width: 7rem;
  text-align: center;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--muted);
}
.compare-row .arrow {
  width: 2.2rem;
  height: 2px;
  background: linear-gradient(90deg, var(--cf), var(--gcp));
}
.compare-row .translate {
  grid-column: 1 / -1;
  margin: 0.25rem 0 0;
  padding-top: 0.75rem;
  border-top: 1px solid var(--line);
  font-size: 0.9rem;
  color: var(--text);
}
.compare-row .translate span {
  color: var(--cf);
  font-family: var(--font-mono);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-right: 0.5rem;
}
.tag {
  display: inline-block;
  padding: 0.15rem 0.45rem;
  border-radius: 6px;
  background: rgba(245, 165, 36, 0.12);
  color: var(--cf);
  font-size: 0.7rem;
  margin-bottom: 0.35rem;
}

.practice-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}
.flash-card, .scenario-card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.2rem;
  min-height: 280px;
}
.meta {
  margin: 0 0 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--gcp);
}
.flash-card h2, .scenario-card h2 {
  margin: 0 0 1rem;
  font-family: var(--font-display);
  font-size: 1.25rem;
  line-height: 1.3;
  letter-spacing: -0.02em;
}
.flash-answer {
  background: rgba(0,0,0,0.28);
  border-left: 3px solid var(--gcp);
  padding: 0.75rem 0.9rem;
  margin-bottom: 1rem;
  font-size: 0.95rem;
  line-height: 1.5;
  color: var(--muted);
}
.flash-actions { display: flex; flex-wrap: wrap; gap: 0.5rem; }

.btn {
  border: 1px solid var(--line);
  background: rgba(255,255,255,0.05);
  color: var(--text);
  font: 500 0.9rem var(--font-body);
  padding: 0.55rem 0.95rem;
  border-radius: 10px;
  cursor: pointer;
  transition: transform 0.15s, background 0.15s;
}
.btn:hover { transform: translateY(-1px); background: rgba(255,255,255,0.09); }
.btn.solid {
  background: linear-gradient(135deg, var(--gcp-deep), #1f4fb8);
  border-color: transparent;
}
.btn.ghost { background: transparent; }

.options { display: flex; flex-direction: column; gap: 0.45rem; margin-bottom: 0.85rem; }
.option {
  text-align: left;
  border: 1px solid var(--line);
  background: rgba(0,0,0,0.25);
  color: var(--text);
  padding: 0.7rem 0.85rem;
  border-radius: 10px;
  cursor: pointer;
  font: 400 0.9rem/1.35 var(--font-body);
}
.option:hover:not(:disabled) { border-color: rgba(91,159,255,0.5); }
.option.is-correct { border-color: var(--ok); background: rgba(61, 214, 140, 0.1); }
.option.is-wrong { border-color: var(--warn); background: rgba(255, 123, 114, 0.08); }
.option:disabled { cursor: default; opacity: 0.95; }
.feedback {
  margin: 0 0 0.85rem;
  font-size: 0.9rem;
  line-height: 1.45;
  color: var(--muted);
}
.progress-line {
  margin-top: 1rem;
  color: var(--muted);
  font-size: 0.85rem;
  font-family: var(--font-mono);
}

.sim-layout {
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 1rem;
  align-items: start;
}
.sim-scripts {
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
}
.sim-script {
  text-align: left;
  border: 1px solid var(--line);
  background: var(--panel);
  color: var(--text);
  padding: 0.75rem 0.85rem;
  border-radius: 12px;
  cursor: pointer;
  font: 500 0.88rem var(--font-body);
}
.sim-script.is-active {
  border-color: rgba(91,159,255,0.55);
  box-shadow: inset 0 0 0 1px rgba(91,159,255,0.25);
}
.sim-script small {
  display: block;
  margin-top: 0.25rem;
  color: var(--muted);
  font-weight: 400;
  font-size: 0.78rem;
}
.sim-stage {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 1.1rem;
  min-height: 420px;
}
.sim-intro h2 {
  margin: 0 0 0.4rem;
  font-family: var(--font-display);
  font-size: 1.3rem;
}
.sim-intro p { margin: 0 0 1rem; color: var(--muted); line-height: 1.45; }
.sim-thread { display: flex; flex-direction: column; gap: 0.65rem; margin-bottom: 1rem; }
.bubble {
  max-width: 92%;
  padding: 0.75rem 0.9rem;
  border-radius: 12px;
  line-height: 1.45;
  font-size: 0.92rem;
}
.bubble.customer {
  align-self: flex-start;
  background: rgba(245, 165, 36, 0.1);
  border: 1px solid rgba(245, 165, 36, 0.25);
}
.bubble.you {
  align-self: flex-end;
  background: rgba(91, 159, 255, 0.12);
  border: 1px solid rgba(91, 159, 255, 0.28);
}
.bubble .who {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.3rem;
  opacity: 0.75;
}
.sim-input label {
  display: block;
  font-size: 0.8rem;
  color: var(--muted);
  margin-bottom: 0.35rem;
}
.sim-input textarea {
  width: 100%;
  resize: vertical;
  border-radius: 10px;
  border: 1px solid var(--line);
  background: rgba(0,0,0,0.35);
  color: var(--text);
  padding: 0.75rem;
  font: 400 0.95rem/1.45 var(--font-body);
  margin-bottom: 0.65rem;
}
.hint {
  margin: 0.65rem 0 0;
  color: var(--cf);
  font-size: 0.88rem;
  line-height: 1.4;
}
.sim-summary {
  border-top: 1px solid var(--line);
  padding-top: 1rem;
  margin-top: 0.5rem;
}
.sim-summary h3 {
  margin: 0 0 0.5rem;
  font-family: var(--font-display);
}
.sim-summary .score {
  font-family: var(--font-mono);
  color: var(--ok);
  margin-bottom: 0.75rem;
}
.sim-summary .model {
  background: rgba(0,0,0,0.28);
  padding: 0.85rem;
  border-radius: 10px;
  color: var(--muted);
  font-size: 0.9rem;
  line-height: 1.5;
  white-space: pre-wrap;
}

.foot {
  padding: 1rem clamp(1rem, 3vw, 2.5rem) 2rem;
  color: var(--muted);
  font-size: 0.8rem;
  border-top: 1px solid var(--line);
}

@media (max-width: 860px) {
  .practice-layout,
  .sim-layout,
  .compare-row {
    grid-template-columns: 1fr;
  }
  .compare-row .mid { flex-direction: row; min-width: 0; padding: 0.25rem 0; }
  .compare-row .arrow { width: 1.5rem; }
  .tabs { border-radius: 14px; }
}