/* Navy Blue + Black Gradient Stylish Temperature Converter */
:root {
  --bg1: #0f172a; /* dark navy */
  --bg2: #000000; /* black */
  --card-bg: #1e293b; /* slightly lighter navy */
  --card-shadow: 0 8px 24px rgba(0, 0, 0, 0.5);
  --text-dark: #f1f5f9; /* light text */
  --text-light: #94a3b8; /* muted text */
  --primary: #3b82f6; /* bright accent blue */
  --primary-hover: #2563eb;
  --secondary: #8b5cf6; /* purple accent */
  --radius: 12px;
  font-family: "Poppins", "Segoe UI", Roboto, sans-serif;
}

* {
  box-sizing: border-box;
  transition: all 0.2s ease-in-out;
}

body {
  margin: 0;
  min-height: 100vh;
  background: linear-gradient(135deg, var(--bg1), var(--bg2));
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
  color: var(--text-dark);
}

.container {
  width: 100%;
  max-width: 500px;
}

header {
  text-align: center;
  margin-bottom: 20px;
  color: var(--text-dark);
}

h1 {
  margin: 0;
  font-size: 2rem;
  letter-spacing: 0.5px;
  text-shadow: 0 2px 6px rgba(0, 0, 0, 0.5);
}

.lead {
  margin-top: 6px;
  color: var(--text-light);
  font-size: 1rem;
}

.card {
  background: var(--card-bg);
  padding: 24px;
  border-radius: var(--radius);
  box-shadow: var(--card-shadow);
  border: none;
}

label {
  font-weight: 500;
  font-size: 0.9rem;
  color: var(--text-light);
  display: block;
  margin-bottom: 6px;
}

input[type="number"],
select {
  width: 100%;
  padding: 12px;
  font-size: 1rem;
  border-radius: var(--radius);
  border: 1px solid #334155;
  outline: none;
  margin-bottom: 14px;
  background: #0f172a;
  color: var(--text-dark);
}

input[type="number"]:focus,
select:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.3);
}

.row {
  display: flex;
  gap: 12px;
  margin-bottom: 14px;
}

.col {
  flex: 1;
}

.buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 14px;
  justify-content: center;
}

.btn {
  padding: 10px 18px;
  border-radius: var(--radius);
  font-weight: 600;
  border: none;
  cursor: pointer;
  color: white;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
}

.btn:hover {
  background: linear-gradient(135deg, var(--primary-hover), var(--secondary));
  transform: translateY(-2px);
}

.btn.outline {
  background: transparent;
  border: 2px solid var(--primary);
  color: var(--primary);
  box-shadow: none;
}

.btn.outline:hover {
  background: var(--primary);
  color: white;
}

.btn.ghost {
  background: #1e293b;
  color: var(--text-dark);
  border: 1px dashed #64748b;
}

.btn.ghost:hover {
  background: #334155;
}

.result {
  padding: 14px;
  border-radius: var(--radius);
  background: linear-gradient(90deg, #1e293b, #0f172a);
  border: 1px solid #334155;
  font-weight: 700;
  font-size: 1.1rem;
  text-align: center;
  color: var(--primary-hover);
  box-shadow: inset 0 0 8px rgba(59, 130, 246, 0.15);
}

.hint {
  margin-top: 12px;
  text-align: center;
  color: var(--text-light);
  font-size: 0.85rem;
}

@media (max-width: 420px) {
  .row {
    flex-direction: column;
  }
  .buttons {
    flex-direction: column;
  }
}