$(function(){

  if ($("#page-index").length){
    let snum = 1;
    let slide_base = $("#catch");

    let slider = function () {
      if (snum < 3) {
        slide_base.removeClass("s" + snum);
        snum++;
        slide_base.addClass("s" + snum);
      }
      else {
        slide_base.removeClass("s" + snum);
        snum = 1;
        slide_base.addClass("s" + snum);
      }
    }
    let slider_timer = setInterval(slider, 4000);
  }

  $("#page-index #scroll").click(function () {
    scroll_screen("#about");
    return false;
  });

  function scroll_screen(id, speed) {
    var target_height = $(id).offset().top;
    target_height -= 50;
    $('html,body').animate({ scrollTop: target_height}, speed);
  }

 });