It's hard to describe Onion Assault, it doesn't really do anything wrong but it also lacks a spark to make it interesting.

Some stages work better than others, the railcart level with cannons is very fun but then there is also a swaying tree one that has this weird inertia with your movement. I also feel some parts can be frustrating, especially with a lives system that in modern games feel very unnecessary.

If you are looking for a short burst of "Super Mario Bros. 2"-like gameplay, you can probably enjoy Onion Assault, just don't expect anything that will blow your mind.