* { margin: 0; padding: 0; box-sizing: border-box; }
body { font-family: 'Inter', sans-serif; background: #282c34; color: #fff; display: flex; justify-content: center; align-items: center; min-height: 100vh; }
.container { background: #1c2025; padding: 30px; border-radius: 10px; box-shadow: 0 4px 15px rgba(0,0,0,0.5); text-align: center; width: 350px; }
h1 { font-size: 24px; margin-bottom: 20px; color: #61dafb; }
.input-group { display: flex; flex-direction: column; gap: 10px; }
input { padding: 10px; border: 2px solid #333; border-radius: 5px; background: #282c34; color: #fff; outline: none; }
input:focus { border-color: #61dafb; }
button { padding: 10px; background: #61dafb; color: #1c2025; border: none; border-radius: 5px; cursor: pointer; font-weight: bold; }
button:hover { background: #4fa8c7; }
.result { margin-top: 15px; font-weight: bold; min-height: 24px; }
.valid { color: #4CAF50; }
.invalid { color: #F44336; }