:root {
  --primary: #6366f1;
  --primary-gradient: linear-gradient(135deg, #6366f1 0%, #a855f7 100%);
  --background: #0f172a;
  --card-bg: rgba(255, 255, 255, 0.05);
  --text-primary: #fff;
  --text-secondary: #94a3b8;
}

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

body {
  font-family: 'Inter', sans-serif;
  margin: 0;
  padding: 0;
  background: var(--background);
  color: var(--text-primary);
}

header {
  background: var(--primary-gradient);
  padding: 2rem;
  box-shadow: 0 4px 30px rgba(0, 0, 0, 0.1);
}

header h1 {
  font-weight: 700;
  font-size: 2.5rem;
  margin: 0;
}

.container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 2rem;
  padding: 2rem;
  max-width: 1400px;
  margin: 0 auto;
}

.card {
  background: var(--card-bg);
  backdrop-filter: blur(16px);
  border-radius: 16px;
  border: 1px solid rgba(255, 255, 255, 0.1);
  padding: 1.5rem;
  transition: all 0.3s ease;
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.2);
}

.card h2 {
  color: var(--text-primary);
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: 1rem;
}

.card p {
  color: var(--text-secondary);
  line-height: 1.6;
}

.card button {
  background: var(--primary-gradient);
  color: white;
  border: none;
  padding: 0.75rem 1.5rem;
  margin: 0.5rem;
  border-radius: 8px;
  font-weight: 500;
  transition: all 0.3s ease;
  cursor: pointer;
}

.card button:hover {
  opacity: 0.9;
  transform: translateY(-2px);
}

.test-area {
  margin-top: 1rem;
}

.test-area textarea {
  width: 100%;
  min-height: 120px;
  padding: 1rem;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 8px;
  color: var(--text-primary);
  font-family: 'Inter', monospace;
  resize: vertical;
}

.solution {
  margin-top: 1rem;
  padding: 1rem;
  background: rgba(255, 255, 255, 0.05);
  border-radius: 8px;
  border: 1px solid rgba(255, 255, 255, 0.1);
}