I am making an classic 2D arcade ball game. There will be 100 levels in this game. And after the 80th level passing the level by doing some arcade stuff will be very difficult.

For example level 100 will be the most difficult level and if I can't pass this level with manual testing (I am not very skillful), how can I know without manual testing if the 100th level can be passed?

(I don't want to make an impossible level. I just want to make a very difficult level.)