body{
 background:#020617;
 color:#e5e7eb;
 font-family:Arial;
 text-align:center;
 padding-top:30px;
}

.panel{
 width:380px;
 margin:auto;
 background:#0f172a;
 padding:20px;
 border-radius:12px;
 box-shadow:0 0 20px #000;
}

#counter{
 font-size:48px;
 margin:20px 0;
 color:#22c55e;
}

button{
 padding:10px 18px;
 margin:5px;
 border:none;
 border-radius:6px;
 font-weight:bold;
 cursor:pointer;
}

#startBtn{background:#22c55e;}
#stopBtn{background:#ef4444;color:#fff;}
.reset{background:#64748b;color:#fff;}

input{
 padding:8px;
 border-radius:6px;
 text-align:center;
 width:80px;
}

.hidden{display:none;}