canvas {
      position: fixed;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      z-index: -1;
    }


    .overlay {
        position: fixed;
        top: 0;
        left: 0;
        width: 100vw;
        height: 100vh;
        background-color: rgba(0, 0, 0, 0.5); /* 0.5 = 50% d’opacité */
        z-index: 0;
    }