html, body {
    height: 100%;
    margin: 0;
}

/* viewport-vullende container */
.center-page {
    min-height: 100vh;          /* vult het scherm */
    display: grid;
    place-items: center;        /* center horizontaal + verticaal */
    text-align: center;         /* centreren van tekstregels */
    padding: 1rem;
    box-sizing: border-box;
    background: #f7f7f9;
    font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
}
    
.card {
    max-width: 800px;
    width: 100%;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 6px 20px rgba(0,0,0,0.06);
    background: white;
}

.btn {
  background-color: #555555;
  border: none;
  color: #FFFFFF;
  padding: 15px 32px;
  text-align: center;
  transition-duration: 0.4s;
  margin: 8px 0;
  text-decoration: none;
  font-size: 16px;
  cursor: pointer;
}

.btn-round {
  border-radius: 12px;
  padding: 20px;
}

.btn-stop {
  background-color: #EE4B2B;
}

.btn-play {
  background-color: #097969;
}