:root {
  --primary: #2563eb;
  --accent: #3b82f6;
  --bg: #f9fafb;
  --text: #1f2937;
  --muted: #6b7280;
}

* {
  box-sizing: border-box;
}

body {
  font-family: 'Segoe UI', Tahoma, sans-serif;
  background: var(--bg);
  color: var(--text);
  margin: 0;
  padding: 0;
}

nav {
  background: var(--primary);
  box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

nav ul {
  list-style: none;
  margin: 0;
  padding: 0.5rem 1rem;
  display: flex;
  gap: 1rem;
}

nav a {
  color: #fff;
  text-decoration: none;
  padding: 0.5rem 0.75rem;
  border-radius: 4px;
}

nav a:hover,
nav a.active {
  background: var(--accent);
}

.container {
  width: 90%;
  max-width: 960px;
  margin: 1.5rem auto;
}

main {
  background: #fff;
  padding: 1.5rem;
  border-radius: 8px;
  box-shadow: 0 2px 6px rgba(0,0,0,0.05);
}

h1 {
  margin-top: 0;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 1rem;
}

th, td {
  padding: 0.75rem;
  border-bottom: 1px solid #e5e7eb;
}

th {
  background: var(--primary);
  color: #fff;
  text-align: left;
}

button {
  background: var(--primary);
  color: #fff;
  border: none;
  padding: 0.5rem 1rem;
  border-radius: 4px;
  cursor: pointer;
}

button:hover {
  background: var(--accent);
}

input, select, textarea {
  padding: 0.5rem;
  border: 1px solid #d1d5db;
  border-radius: 4px;
  width: 100%;
}

form {
  display: grid;
  gap: 1rem;
}

.error {
  color: #dc2626;
}

.footer {
  text-align: center;
  padding: 1rem;
  margin-top: 2rem;
  color: var(--muted);
}

@media (max-width: 600px) {
  nav ul {
    flex-direction: column;
  }

  table, thead, tbody, th, td, tr {
    display: block;
  }

  th, td {
    padding: 0.5rem;
  }
}