So many people talking about figuring out how to play but nobody seems to have actually explained it yet so I'll have a crack.
Use space to shoot the numbers scrolling up the screen, use blue mode to add to the number and red to subtract (the value added or subtracted is shown beside the player character, up/down or w/s are used to increment/decrement this). If you cancel/zero the number out it disappears and you gain some money, which can be used to buy more ammo, ammo capacity or increment points. If the numbers reach the top they add to the bar they came from (so negative values make it smaller).
It seems the game ends when a bar reaches the top, which led to a soft lock on my second go as I ran out of ammo and money but the values were more or less balancing so it just kept going. If there's no way to gain currency without ammo then there should probably be another loss condition to account for this.
I like the idea and it was fun for a while but it has a messed up difficulty curve where it's frantic for a bit but if you stay in red mode and just let the negative numbers go you don't seem to be able to really lose.