body{
margin:0;
background:black;
color:white;
font-family:Arial;
overflow:hidden;
text-align:center;
}

.center{
height:100vh;
display:flex;
justify-content:center;
align-items:center;
flex-direction:column;
padding:20px;
}

button{
padding:15px 30px;
font-size:18px;
border:none;
border-radius:30px;
background:purple;
color:white;
margin-top:20px;
cursor:pointer;
}

.hidden{
display:none;
}

#text{
font-size:20px;
line-height:1.6;
max-width:90%;
margin-top:20px;
}

#subtopic{
font-size:24px;
margin-bottom:20px;
color:yellow;
text-shadow: 0 0 10px yellow, 0 0 20px gold;
animation: glow 1.5s infinite alternate;
}

@keyframes glow{
from{text-shadow: 0 0 10px yellow, 0 0 20px gold;}
to{text-shadow: 0 0 20px yellow, 0 0 40px gold;}
}