body {
    margin: 0;
    font-family: sans-serif;
    background: #0f172a;
    color: #fff;
    text-align: center;
}
.container { padding: 20px; }
button {
    padding: 15px 30px;
    font-size: 18px;
    border: none;
    border-radius: 10px;
    background: #22c55e;
    color: #000;
    cursor: pointer;
}
#breathCircle {
    width: 120px;
    height: 120px;
    margin: 30px auto;
    border-radius: 50%;
    background: #38bdf8;
    transition: transform 4s ease-in-out;
}
.breathe { transform: scale(1.8); }
p { font-size: 18px; }