Well I made an account so I could play, and your difficulty curve is maddening. Levels 1 and 2 are trivial cake walks and then level 3 is practically impossible and incredibly irritating. If I had a shotgun or machine gun in level 3 it would be possible, but when you get 1 credit per enemy and any decent weapon costs at least 475, well thatās what we call a bad difficulty curve. You simply canāt kill all the blob spawners and blobs in level 3 with a shitty old handgun. Not to mention that the spawners have an unfair amount of HP and can also beat the bejeezus out of you, and if you run out the room oftentimes when you try to run back in a bug immediately forces you out again, so if you were lucky to make good progress youāre screwed anyway and have to restart the level.
So my advice: tone down the power of the slime spawners (make them stationary, make it so they canāt fight back, and give them less HP), and/or drastically decrease the difficulty of zone 3 or increase the money you get beforehand. Also recharging your life every time you die / restart a level is a good idea.

That, or have the tougher enemies drop more money. Or both. And make the money stay a little while longer.