:root {
  --bg: #eef3f8;
  --panel: #ffffff;
  --ink: #0f172a;
  --muted: #64748b;
  --line: #cbd5e1;
  --ok: #10b981;
  --bad: #b91c1c;
  --accent: #0b57d0;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "DM Sans", sans-serif;
  color: var(--ink);
  background:
    radial-gradient(circle at 10% 15%, #c7ddff 0%, transparent 30%),
    radial-gradient(circle at 90% 85%, #d1fae5 0%, transparent 25%),
    var(--bg);
  padding: 2rem;
}

.page-title {
  max-width: 1100px;
  margin: 0 auto 1rem;
}

.page-title h1 {
  margin: 0;
  font: 700 clamp(1.3rem, 2.5vw, 2rem) "Space Grotesk", sans-serif;
  color: #0b3a7e;
}

.lab-home {
  color: inherit;
  text-decoration: none;
}

.lab-home:hover {
  text-decoration: underline;
}

.app {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0;
}

.control-bar {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: 0 12px 30px rgba(15, 23, 42, 0.08);
  padding: 16px;
}

.control-bar h1 {
  margin: 0;
  font: 700 clamp(1.4rem, 3vw, 1.8rem) "Space Grotesk", sans-serif;
}

.control-bar p {
  margin: 6px 0 0;
  color: var(--muted);
}

label {
  font-weight: 700;
  font-size: 0.92rem;
  margin-bottom: 4px;
  display: block;
}

button,
input[type="text"],
input[type="number"] {
  border-radius: 10px;
}

button {
  border: 1px solid #bdc8da;
  background: #ffffff;
  color: var(--ink);
  font-weight: 800;
  padding: 10px 12px;
  cursor: pointer;
  transition: transform 120ms ease, box-shadow 120ms ease;
}

button:hover:not(:disabled) {
  transform: translateY(-1px);
  box-shadow: 0 6px 12px #00112f1f;
}

button:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}

#runBtn {
  background: linear-gradient(180deg, #22c55e, #0f766e);
  color: #fff;
  border-color: #0d6b64;
}

#resetBtn {
  background: #f3f4f6;
}

.layout {
  margin-top: 12px;
  display: grid;
  gap: 12px;
  grid-template-columns: 1fr 1fr;
}

.layout.locked {
  opacity: 0.55;
  pointer-events: none;
}

.student-gate {
  margin-top: 12px;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: 0 12px 30px rgba(15, 23, 42, 0.08);
  padding: 12px;
}

.student-gate h2 {
  margin: 0;
  font-size: 1.05rem;
}

.student-gate p {
  margin: 8px 0 0;
  color: var(--muted);
}

.student-form {
  margin-top: 10px;
}

.input-panel,
.output-panel {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: 0 12px 30px rgba(15, 23, 42, 0.08);
  padding: 12px;
}

.field + .field {
  margin-top: 10px;
}

.field input {
  width: 100%;
  border: 1px solid #c8d1e0;
  padding: 10px;
  font-size: 0.95rem;
  background: #fff;
}

#startActivityBtn {
  margin-top: 12px;
  background: linear-gradient(180deg, #1d4ed8, #1e40af);
  color: #fff;
  border-color: #1e3a8a;
}

.actions {
  margin-top: 12px;
  display: flex;
  gap: 8px;
}

.hint {
  margin: 10px 0 0;
  color: var(--muted);
  font-size: 0.9rem;
}

.examples {
  margin-top: 12px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: #f8fbff;
  padding: 10px;
}

.examples h3 {
  margin: 0 0 8px;
  font-size: 0.95rem;
}

.example-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
}

.example-btn {
  border: 1px solid #bfd3f6;
  background: #ffffff;
  color: #1e3a8a;
  padding: 8px 10px;
  font-weight: 700;
  font-size: 0.86rem;
}

.status-line {
  font-weight: 700;
  margin-bottom: 10px;
  min-height: 22px;
}

.status-line.ok {
  color: var(--ok);
}

.status-line.error {
  color: var(--bad);
}

.summary {
  margin-bottom: 10px;
  border: 1px solid #a8cfb9;
  background: #ecfdf3;
  border-radius: 10px;
  padding: 10px;
  font-size: 0.92rem;
}

.summary.error {
  border-color: #efb4b4;
  background: #fef2f2;
}

.tree-wrap h2,
.log-wrap h2 {
  margin: 0 0 8px;
  font-size: 1rem;
}

.tree-output {
  border: 1px dashed #bcc8db;
  border-radius: 10px;
  padding: 10px;
  background: #f9fcff;
  min-height: 220px;
  overflow: auto;
}

.tree-output ul {
  margin: 4px 0 0 18px;
  padding-left: 14px;
}

.tree-output li {
  margin: 5px 0;
  line-height: 1.35;
}

.tree-node-base {
  color: #0f766e;
  font-weight: 700;
}

.tree-node-error {
  color: #b91c1c;
  font-weight: 700;
}

.analysis-log {
  margin: 8px 0 0;
  padding-left: 18px;
  display: grid;
  gap: 7px;
  max-height: 180px;
  overflow-y: auto;
}

.analysis-log li {
  background: #fff;
  border: 1px solid #dbe4f2;
  border-radius: 8px;
  padding: 6px 8px;
  font-size: 0.88rem;
}

.gate-status {
  margin: 10px 0 0;
  min-height: 20px;
  color: var(--ok);
  font-weight: 700;
}

.gate-status.error {
  color: var(--bad);
}

.page-footer {
  max-width: 1100px;
  margin: 1rem auto 0;
  font-size: 0.9rem;
  color: #334155;
}

.page-footer a {
  color: #0b57d0;
  text-decoration: none;
  font-weight: 700;
}

.page-footer a:hover {
  text-decoration: underline;
}

.hidden {
  display: none;
}

@media (max-width: 980px) {
  body {
    padding: 1rem;
  }

  .layout {
    grid-template-columns: 1fr;
  }

  .example-grid {
    grid-template-columns: 1fr;
  }
}