BRE03

document.addEventListener('DOMContentLoaded', function() {
    let button = document.getElementById("ex3Btn");

    button.addEventListener("click", function () {
        let grid = document.getElementById("grid");

        //grid.classList.remove("grid-2");
        //grid.classList.add("grid-3");

        grid.classList.toggle("grid-2");
        grid.classList.toggle("grid-3");
    })
})