I was going to make a game where you drive a truck in 2D and have to prevent the items from falling out, but that felt unoriginal. Like there would be at least a dozen games with a similar premise other people made.

Instead, I'm going to make a 3D fantasy game where you have to deliver a magical orb to a wizard or priest so he can use it to perform a ritual to banish the demon lord from the kingdom. It'll have Super Mario Bros 2 inspired gameplay where you have to hold the item, which affects your movement and jumping. You can also throw the orb to attack enemies or to move it past a difficult jump that you wouldn't be able to pull off while holding it. There may be other things like using the orb to weigh down a switch or standing on it to reach higher places.