Contrasting colors/shapes can be really useful from my understanding? If you want something readable but still cohesive, I've heard that taking a bright contrasting palette and putting a hue over it is a quick "hack" to make it blend better, though I admittedly haven't tried it.
I usually use the game to guide the visual design. I start with the worst programmer art imaginable (circles, stretched triangles, capsules at weird angles) and upgrade only once it becomes clear the existing art won't cut it. And above all, I try to make things readable: make sure the player can see and differentiate themselves, hazards, and goals/powerups as easily as possible. But if there's one thing I've learned from my artist friends, it's that the final product never looks exactly like what's in your head - part of the artistic process is learning how to incorporate quirks and limitations rather than fight them (easier said than done). The game art you show looks excellent though!
Levels where one player has to make a way for the other to continue? Levels where the players need to do something in sync, or otherwise have to coordinate their movements? Levels where the speedy player has to race a condition and/or the jumping player needs to complete some parkour challenge in a time limit?
the duality of artist
the duality of artist
