* { box-sizing: border-box }
body {
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  margin: 0;
  padding: 20px;
  transition: background-color 0.3s, color 0.3s;
}
.light { background-color: #f6f7fb; color: #111 }
.dark { background-color: #121417; color: #eaeaea }

.container {
  max-width: 860px;
  margin: auto;
  padding: 20px;
  border-radius: 16px;
  box-shadow: 0 6px 20px rgba(0,0,0,0.08);
  transition: background-color 0.3s, color 0.3s, box-shadow 0.3s;
}
.light .container { background: #fff }
.dark .container { background: #1a1f24; box-shadow: 0 6px 20px rgba(0,0,0,0.3) }

nav {
  background: linear-gradient(90deg,#4CAF50,#2e7d32);
  padding: 10px 16px;
  margin-bottom: 20px;
  border-radius: 0 0 12px 12px;
}
nav ul {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  gap: 10px;
  align-items: center;
  justify-content: center;
  flex-wrap: wrap;
}
nav ul li a, nav ul li button {
  color: #fff;
  text-decoration: none;
  padding: 10px 14px;
  border-radius: 10px;
  cursor: pointer;
  border: none;
  background: rgba(255,255,255,0.12);
}
nav ul li a:hover, nav ul li button:hover { background: rgba(255,255,255,0.22) }

h1, h2 { text-align: center; margin: 10px 0 16px }

input, select, button {
  width: 100%;
  margin: 10px 0;
  padding: 12px 14px;
  border-radius: 10px;
  border: 1px solid transparent;
  outline: none;
  transition: background-color 0.3s, color 0.3s, border-color 0.3s;
}
.light input, .light select { background: #fff; color: #111; border-color: #e5e7eb }
.dark input, .dark select { background: #2a3036; color: #fff; border-color: #3a424a }

button {
  background-color: #4CAF50;
  color: #fff;
  border: none;
  cursor: pointer;
  font-weight: 600;
}
button.secondary { background-color: #374151 }
button:disabled { opacity: 0.6; cursor: not-allowed }

.row { display: flex; gap: 10px }
.row button { flex: 1 }

.loader {
  border: 5px solid rgba(255,255,255,0.25);
  border-top: 5px solid #3498db;
  border-radius: 50%;
  width: 30px;
  height: 30px;
  animation: spin 1s linear infinite;
  margin: 10px auto;
}
@keyframes spin { 0% { transform: rotate(0deg) } 100% { transform: rotate(360deg) } }

.result-item {
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px dashed rgba(0,0,0,0.15);
  margin: 8px 0;
}
.dark .result-item { border-color: rgba(255,255,255,0.25) }
.muted { opacity: 0.7 }

@media (max-width: 640px) {
  .container { padding: 14px }
  nav ul { justify-content: space-between }
}