body { font-family: Arial; text-align: center; margin: 0; padding: 40px; background: #f5f5f5; }
#timer { font-size: 120px; font-weight: bold; color: #4CAF50; margin: 40px 0; }
.btn { padding: 15px 30px; font-size: 18px; background: #2196F3; color: white; border: none; border-radius: 5px; cursor: pointer; margin: 10px; }