.stopwatch,header{text-align:center}*{margin:0;padding:0;box-sizing:border-box;font-family:'Segoe UI',Tahoma,Geneva,Verdana,sans-serif}body{background:#f9f9f9;display:flex;flex-direction:column;align-items:center;padding:20px;color:#333}header{margin-bottom:30px}header h1{font-size:2rem;color:#1a73e8}.stopwatch{background:#fff;padding:40px 30px;border-radius:16px;box-shadow:0 4px 20px rgba(0,0,0,.1);max-width:400px;width:100%}#display{font-size:3rem;margin-bottom:20px}.buttons button{background:#1a73e8;color:#fff;border:none;padding:12px 24px;margin:0 5px;font-size:1rem;border-radius:8px;cursor:pointer;transition:background .3s}.buttons button:hover{background:#155ec2}.article{margin-top:40px;max-width:800px;text-align:left;line-height:1.6}.article h2{margin-bottom:10px;font-size:1.5rem;color:#111}.article p{margin-bottom:20px}@media (max-width:600px){.stopwatch{padding:20px}#display{font-size:2.5rem}}