*{
    margin:0;
    padding:0;
    box-sizing:border-box;
    font-family:'Segoe UI',sans-serif;
}

body{
    display:flex;
    justify-content:center;
    align-items:center;
    min-height:100vh;
    background:linear-gradient(135deg,#4facfe,#00f2fe);
    transition:0.4s;
}

.container{
    background:white;
    width:90%;
    max-width:500px;
    padding:30px;
    border-radius:20px;
    text-align:center;
    box-shadow:0 8px 25px rgba(0,0,0,0.2);
}

h1{
    margin-bottom:15px;
}

#datetime{
    margin-bottom:15px;
    font-size:18px;
    color:#555;
}

#display{
    font-size:55px;
    font-weight:bold;
    margin:25px 0;
    color:#222;
}

.btn-group{
    display:flex;
    flex-wrap:wrap;
    justify-content:center;
    gap:10px;
}

button{
    padding:12px 18px;
    border:none;
    border-radius:8px;
    cursor:pointer;
    font-size:15px;
    transition:0.3s;
}

button:hover{
    transform:scale(1.05);
}

#startBtn{
    background:#28a745;
    color:white;
}

#pauseBtn{
    background:#ffc107;
}

#resetBtn{
    background:#dc3545;
    color:white;
}

#lapBtn{
    background:#007bff;
    color:white;
}

#themeBtn{
    margin-top:15px;
    background:#222;
    color:white;
}

.laps{
    margin-top:20px;
    text-align:left;
}

.laps ul{
    max-height:180px;
    overflow-y:auto;
}

.laps li{
    list-style:none;
    padding:8px;
    margin:5px 0;
    background:#f1f1f1;
    border-radius:5px;
}

.dark-mode{
    background:#121212;
}

.dark-mode .container{
    background:#1e1e1e;
    color:white;
}

.dark-mode #display{
    color:#00ff88;
}

.dark-mode .laps li{
    background:#333;
}