body { text-align: center; font-family: Arial; background: white; }
input, button { margin: 10px; padding: 10px; font-size: 18px; }
#checkinBtn { background: #00FF00; color: white; border: none; border-radius: 50%; width: 150px; height: 150px; font-size: 24px; cursor: pointer; }
#loginBtn, #campusLoginBtn, #shareBtn { background: blue; color: white; }
#tips { color: gray; }
#loading { font-size: 20px; color: green; }