click the green flag and then click the down arrow to start Arrow keys to move full screen not recommended! Also, there are more cubes so click 2,3,4, and 5 to chose one of those but if you chose 5 you have to click one to be able to choose a different one :) I recommend 3!
My bro @MidnightCoveGaming with platformer physics/some coding if you haven't seen his stuff you should really check it out! Also sometimes you may get stuck in a wall so the way to get out is holding the up arrow and left or right arrow (whichever one is going back into the level) please like and fave! :)