itch.io

In my own web engine, the key to fixing this was adding "preventDefault()" to my key event handling method. FWIW, this is my method:

HandleKeyDown: function (e) {

                var keyCode = e.keyCode;

                [....some code to store / handle key input here...]

                if (keyCode !== Key.F11) {

                    e.preventDefault();

                }

            }

But more importantly, if you know what term to google for, you can find the solution. :-) 

This seems helpful in your case:

https://www.construct.net/en/forum/construct-3/how-do-i-8/keep-arrow-keys-scroll...