On the third level the arrow keys were swapped - I had to press the down key to move up and the up key to move down - when moving vertically. They worked as I expected when moving horizontally. You need a skip tutorial button - people who regularly play games, do not like hand-holding tutorials.
(I don't play violent games, so I liked your concept (teaching maths), but shooting at a tank and being shot at - put me off before I could properly evaluate the game.)