Neat concept. Visually the game looks really nice with the contrasting colorscheme and I like the challenge of having to pay attention to both sides. Some small changes I would do:
Add some OST. Doesn't need to be anything fancy, just something to set the tone.
Allow me to input questions for bonus points instead of waiting for the timer to run out. For example the maths one, let me press space if it's on the left and enter if it's on the right to answer the question quicker in exchange for some points. If I'm having trouble with the other side at that point, I would simply let the timer run out but if I'm managing the other one, just let me get to the next one. (Sidenote: You could also use them for actions in games like the Lunar Shield or Space Invader)
Give me a toggle that indicates wether the games jump directly into it without showing me the explanation. It's just wasted time doing nothing, I'm not going to read it after the first time playing the game.
Other than that, I find the Flap and Paddle to be the ones that cause me the most trouble. Paddle is fine how it is, but MAYBE Flap should be more leniant, MAYBE. That depends on how hard you want to make the game, right now it is fine but if I HAD to change one, Flap would be it.
Keep adding games to have even more combinations and you could have a neat minigames game ala Wario Ware.
In terms of other games: Some sorting game where you have to match the symbol to some other 4 symbols that keep changing? One where you have to simply press what is beeing shown (IE Input this 20 button sequence). One where you have to aim a a reticule at something? A Button masher? They don't need to be all super interesting, I think in this case variety matters more than quality TBH.