:root {
  --bg: #f4f7fb;
  --card: #ffffff;
  --primary: #13c2dd;
  --primary-dark: #13c2dd;
  --text: #1f2937;
  --muted: #6b7280;
  --border: #e5e7eb;
  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: Arial, Helvetica, sans-serif;
  background: linear-gradient(135deg, #eef2ff 0%, #f8fafc 100%);
  color: var(--text);
  display: grid;
  place-items: center;
}

.container {
  width: min(100%, 480px);
  padding: 24px;
}

.card {
  background: var(--card);
  border-radius: 20px;
  box-shadow: 0 20px 40px rgba(79, 70, 229, 0.12);
  padding: 32px 24px;
}

.header {
  text-align: center;
  margin-bottom: 24px;
}

.eyebrow {
  margin: 0 0 8px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--primary);
  font-size: 12px;
  font-weight: 700;
}

h1 {
  margin: 0;
  font-size: 2rem;
}

.form {
  display: grid;
  gap: 18px;
}

.field-group {
  display: grid;
  gap: 8px;
}

label {
  font-weight: 700;
  font-size: 0.95rem;
}

input {
  width: 100%;
  padding: 14px 16px;
  border: 1px solid var(--border);
  border-radius: 12px;
  font-size: 1rem;
  outline: none;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 4px rgba(79, 70, 229, 0.1);
}

button {
  border: none;
  border-radius: 12px;
  background: var(--primary);
  color: white;
  font-weight: 700;
  font-size: 1rem;
  padding: 14px 18px;
  cursor: pointer;
  transition: background 0.2s ease, transform 0.2s ease;
}

button:hover {
  background: var(--primary-dark);
  transform: translateY(-1px);
}

.result {
  margin-top: 28px;
  background: #f8fafc;
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 20px 18px;
  text-align: center;
}

.result-label {
  margin: 0;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.75rem;
  font-weight: 700;
}

#bmi-value {
  margin: 12px 0 8px;
  font-size: 2.2rem;
  color: var(--primary-dark);
}

#bmi-category {
  margin: 0;
  color: var(--text);
  font-weight: 600;
}