:root {
  --bg: #f8fafc;
  --card: #ffffff;
  --text: #0f172a;
  --muted: #64748b;
  --primary: #2563eb;
  --border: #e2e8f0;
  --shadow: 0 10px 24px rgba(15, 23, 42, 0.08);
  --radius: 16px;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: "Inter", "Segoe UI", sans-serif;
}

body {
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  padding: 28px 18px;
}

.demo-page {
  max-width: 1080px;
  margin: 0 auto;
  display: grid;
  gap: 16px;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
}

.demo-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 14px;
}

.demo-header h1 {
  font-size: 30px;
  line-height: 1.2;
}

.demo-header p {
  margin-top: 8px;
  color: var(--muted);
}

.back-link {
  text-decoration: none;
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: 12px;
  padding: 10px 14px;
  font-weight: 600;
  background: #fff;
}

.input-section h2,
.explanation-panel h2 {
  font-size: 18px;
}

.section-note {
  margin-top: 8px;
  color: var(--muted);
}

.status-text {
  margin-top: 12px;
}

.status-text.error {
  color: #b91c1c;
}

.input-row {
  margin-top: 14px;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 10px;
}

.input-row input {
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px 14px;
  font-size: 15px;
  color: var(--text);
}

.input-row button {
  border: none;
  border-radius: 12px;
  padding: 12px 18px;
  background: var(--primary);
  color: #ffffff;
  font-weight: 600;
  cursor: pointer;
}

.demo-steps {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 14px;
}

.demo-steps h3 {
  font-size: 16px;
}

.placeholder-box {
  margin-top: 12px;
  min-height: 170px;
  border: 1px dashed #cbd5e1;
  border-radius: 12px;
  background: linear-gradient(180deg, #f8fafc 0%, #f1f5f9 100%);
  padding: 12px;
  overflow: auto;
}

.result-row {
  display: grid;
  grid-template-columns: 120px 1fr;
  gap: 8px;
  padding: 8px 0;
  border-bottom: 1px solid #e2e8f0;
  font-size: 14px;
}

.result-row:last-child {
  border-bottom: 0;
}

.result-label {
  color: var(--muted);
  font-weight: 600;
}

.result-value {
  color: var(--text);
  word-break: break-word;
}

.result-empty {
  color: var(--muted);
  font-size: 14px;
}

.explanation-panel p {
  margin-top: 10px;
  color: var(--muted);
  line-height: 1.7;
}

@media (max-width: 900px) {
  .demo-steps {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 640px) {
  .demo-header {
    flex-direction: column;
  }

  .demo-header h1 {
    font-size: 24px;
  }

  .input-row {
    grid-template-columns: 1fr;
  }
}