:root {
  --bg: #FFE6F2;
  --surface: #FFFFFF;
  --surface-2: #FFD1EA;
  --border: #FF9FD1;
  --text: #7A1955;
  --muted: #C2569D;
  --cyan: #FF2CA2;
  --amber: #FF6EC7;
  --violet: #E5399B;
  --green: #17B884;
  --red: #E8306B;
  --mono: 'JetBrains Mono', monospace;
  --display: 'Space Grotesk', sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--display);
  min-height: 100vh;
  position: relative;
}

.bg-grid {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image:
    linear-gradient(to right, rgba(255, 44, 162, 0.08) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(255, 44, 162, 0.08) 1px, transparent 1px);
  background-size: 42px 42px;
  mask-image: radial-gradient(ellipse 80% 60% at 50% 0%, black 40%, transparent 100%);
}

header.topbar {
  position: relative;
  z-index: 2;
  padding: 28px 40px 0 40px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 24px;
}
.brand-mark {
  font-size: 30px;
  color: var(--cyan);
  line-height: 1;
}
.brand-title {
  font-size: 20px;
  font-weight: 700;
  letter-spacing: 0.02em;
}
.brand-sub {
  font-size: 12.5px;
  color: var(--muted);
  font-family: var(--mono);
  margin-top: 2px;
}

.tabs {
  display: flex;
  gap: 4px;
  border-bottom: 1px solid var(--border);
}
.tab {
  background: transparent;
  border: none;
  color: var(--muted);
  font-family: var(--display);
  font-size: 14.5px;
  font-weight: 500;
  padding: 14px 20px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 10px;
  border-bottom: 2px solid transparent;
  transition: color 0.15s, border-color 0.15s;
}
.tab-num {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--cyan);
  opacity: 0.7;
}
.tab:hover { color: var(--text); }
.tab.active {
  color: var(--text);
  border-bottom-color: var(--cyan);
}

main {
  position: relative;
  z-index: 2;
  padding: 36px 40px 60px 40px;
  max-width: 1280px;
  margin: 0 auto;
}

.panel { display: none; }
.panel.active { display: block; animation: fadein 0.25s ease; }
@keyframes fadein { from { opacity: 0; transform: translateY(4px);} to { opacity: 1; transform: none; } }

.panel-head h1 {
  font-size: 26px;
  margin: 0 0 6px 0;
  font-weight: 700;
}
.panel-head p {
  color: var(--muted);
  margin: 0 0 24px 0;
  font-size: 14.5px;
  max-width: 720px;
}

.subtabs {
  display: flex;
  gap: 8px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}
.subtab {
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--muted);
  padding: 8px 16px;
  border-radius: 6px;
  font-family: var(--mono);
  font-size: 12.5px;
  cursor: pointer;
  transition: all 0.15s;
}
.subtab:hover { border-color: var(--cyan); color: var(--text); }
.subtab.active {
  background: var(--surface-2);
  border-color: var(--cyan);
  color: var(--cyan);
}

.subpanel { display: none; }
.subpanel.active { display: block; }

.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}
@media (max-width: 900px) {
  .grid-2 { grid-template-columns: 1fr; }
  main { padding: 24px 18px 48px 18px; }
  header.topbar { padding: 22px 18px 0 18px; }
  .tabs { overflow-x: auto; }
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 22px;
}

label {
  display: block;
  font-size: 12px;
  color: var(--muted);
  font-family: var(--mono);
  margin: 14px 0 6px 0;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}
label:first-child { margin-top: 0; }

.checkbox-label {
  display: flex;
  align-items: center;
  gap: 8px;
  text-transform: none;
  font-size: 13px;
  cursor: pointer;
}
.checkbox-label input { width: auto; }

input[type="text"], textarea {
  width: 100%;
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 10px 12px;
  border-radius: 6px;
  font-family: var(--mono);
  font-size: 13.5px;
  resize: vertical;
}
input[type="text"]:focus, textarea:focus {
  outline: none;
  border-color: var(--cyan);
}

.btn-run {
  margin-top: 18px;
  width: 100%;
  background: var(--cyan);
  color: #FFFFFF;
  border: none;
  padding: 12px 18px;
  border-radius: 6px;
  font-family: var(--display);
  font-weight: 700;
  font-size: 14px;
  cursor: pointer;
  transition: filter 0.15s;
}
.btn-run:hover { filter: brightness(1.1); }

.hint {
  font-size: 12px;
  color: var(--muted);
  margin: 10px 0 0 0;
  line-height: 1.5;
}

.result-card { display: flex; flex-direction: column; }
.result-label {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--cyan);
  margin-bottom: 10px;
}
.result-box {
  font-family: var(--mono);
  font-size: 14px;
  padding: 14px;
  border-radius: 8px;
  background: var(--bg);
  border: 1px solid var(--border);
  margin-bottom: 16px;
  min-height: 24px;
}
.result-box.accept { border-color: var(--green); color: var(--green); }
.result-box.reject { border-color: var(--red); color: var(--red); }

.trace-box {
  font-size: 13px;
  color: var(--text);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px 14px;
  min-height: 40px;
  max-height: 360px;
  overflow: auto;
}
.trace-box.mono { font-family: var(--mono); font-size: 12.5px; white-space: pre-wrap; }
.trace-box.scroll-tall { max-height: 420px; }

.diagram-box {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  min-height: 220px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 16px;
  overflow: auto;
  padding: 10px;
}
.diagram-box.tall { min-height: 320px; }

.trace-step {
  display: flex;
  gap: 10px;
  padding: 6px 0;
  border-bottom: 1px dashed var(--border);
  font-family: var(--mono);
  font-size: 12.5px;
}
.trace-step:last-child { border-bottom: none; }
.trace-step .step-idx { color: var(--muted); min-width: 26px; }
.trace-step .step-sym { color: var(--amber); }
.trace-step .step-state { color: var(--cyan); font-weight: 700; }

.steps-box .step-block {
  border-left: 2px solid var(--violet);
  padding: 10px 0 10px 18px;
  margin-bottom: 18px;
}
.steps-box .step-title {
  font-weight: 700;
  color: var(--violet);
  font-size: 14px;
  margin-bottom: 4px;
}
.steps-box .step-detail {
  color: var(--muted);
  font-size: 12.5px;
  margin-bottom: 8px;
}
.steps-box .step-lines {
  font-family: var(--mono);
  font-size: 12.5px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 10px 12px;
  white-space: pre-wrap;
}

.hier-layer {
  font-family: var(--mono);
  font-size: 12.5px;
  padding: 10px 16px;
  margin: 4px 0;
  border-radius: 6px;
  border: 1px solid var(--border);
  width: 100%;
}
.hier-layer.active {
  border-color: var(--violet);
  background: rgba(229, 57, 155, 0.10);
  color: var(--violet);
  font-weight: 700;
}

.footer {
  position: relative;
  z-index: 2;
  text-align: center;
  color: var(--muted);
  font-family: var(--mono);
  font-size: 11.5px;
  padding: 20px;
  border-top: 1px solid var(--border);
}

code {
  background: var(--surface-2);
  padding: 1px 5px;
  border-radius: 4px;
  color: var(--amber);
}