No problem! Ability points are independent of character lvl, so each playthrough your abilities reset. You can only have maxed out abilities in (I believe) wave 19 & 20, so most of the time you should have something to do on the ability upgrade screen.
Is good but better yet is it's potential, for example your abilities max out at lvl 10, but the guns max out at lvl 20, and the game still brings you to the ability page even though you can't do anything. And of coarse more upgrades is always better(armor, speed, regeneration, different bullet types, barrel lengths(range), character customization. What I'm saying is it's a little bare bones for me.
Not sure what abilities you're talking about- each of your 3 abilities can be upgraded three times, for 1/2/3 AP. So it should take until wave 18 to max out your abilities (3*(1+2+3)). If you're talking about perks, it takes until lvl 19 to max out your perks, with Moneygrubber II being the last perk upgrade. Sorry about not having enough upgrades however- I agree there can never be too much! Glad you enjoyed the game!
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It was a programming language limitation but a friend told me a workaround and I've added support. Try again! :-)