an interesting idea, but....
....but first of all it's not original. I remember a math game that was just like it though I can't remember what it was called (as well as letter invaders in typing tutor which was a bit like this). Next, just having 2 and 3 available is no good when you have several numbers in the hundreds coming at you as well. There just isn't time to hit the 3 button 40 times and the 2 button once or twice to adjust just to take care of ONE of them when there are SEVERAL coming at you, at DIFFERENT SPEEDS, possibly passing through each other, and messing up the modulo 3 adjustment by slamming through and stealing the 2's. You should have some special thing you can do that will let you shoot bigger numbers. Like some mothership flying around at the top of the screen, and if you hit it, you will temporarily be able to shoot, oh, say, 17's by hitting the "x" button for the next minute, and sometimes it won't be 17, it'll be 19, or 23, or 11, or 20.
But the BIG problem is that it goes from terribly easy to impossible without any transition. From dinky 1 digit numbers to suddenly inundations with 3 digit numbers. And what happens while you're firing a fast sequence of 3's at that 120 that is coming fast at you? a "4" or a "5" comes incredibly fast, goes right THROUGH the 120, and absorbs two of the 3's and blows up at you. And even if you do catch it in time, the program often screws up and registers the impact with the number BEHIND it... in fact, it seems to choose the worst possible thing for it to hit whenever there's any ambiguity in that situation, the one that's slightly behind when it's worse, the one that's in front when it's worse. It may indeed be impossible to hit that hypothetical 4 or 5 with ANYTHING if you stop in time. Everything will just go through it and hit the big thing behind it. You need to put in some constraints to the positions and velocities of the incoming numbers to prevent that crap from happening because it's no good the way it is - and it means your performance will mostly be a matter of luck and even supreme skill accompanied by mediocre luck or worse won't get you very far at all.
And THAT is how I know that those cheats who claim to have gotten to level 40 and on, and especially the forgers on the high scores page, are all frauds. No way to do it without unreasonable luck, even if you slow your computer down, for the reasons I gave already. Liars and hackers, the lot of them. Especially anyone who writes in response to say "NverseMpossiblpRadox is wrong, he just isn't as good at math as I am". Nope. Lying fraud. I insult you in advance! And I'm better than you at math too, ha ha!