* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: system-ui, -apple-system, sans-serif;
  background: #f4f4f5;
  color: #18181b;
}
.container {
  max-width: 520px;
  margin: 48px auto;
  padding: 24px;
  background: #fff;
  border-radius: 12px;
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
}
h1 { margin-top: 0; }
form { display: flex; gap: 8px; }
#new-todo { flex: 1; padding: 10px 12px; font-size: 16px; border: 1px solid #d4d4d8; border-radius: 8px; }
button { padding: 8px 12px; border: 1px solid #d4d4d8; background: #fff; border-radius: 8px; cursor: pointer; }
button:hover { background: #f4f4f5; }
.filters { display: flex; gap: 6px; margin: 16px 0; }
.filters button.active { background: #18181b; color: #fff; border-color: #18181b; }
ul { list-style: none; padding: 0; margin: 0; }
li { display: flex; align-items: center; gap: 10px; padding: 10px 0; border-bottom: 1px solid #f4f4f5; }
li span { flex: 1; }
li.completed span { text-decoration: line-through; color: #a1a1aa; }
.delete { border: none; color: #ef4444; font-size: 18px; }
footer { display: flex; justify-content: space-between; align-items: center; margin-top: 16px; color: #71717a; }
.error { display: flex; justify-content: space-between; align-items: center; gap: 8px; margin: 12px 0 0; padding: 8px 12px; background: #fef2f2; color: #b91c1c; border: 1px solid #fecaca; border-radius: 8px; }
.error[hidden] { display: none; }
li input.edit { flex: 1; padding: 4px 8px; font-size: 16px; border: 1px solid #d4d4d8; border-radius: 6px; }