A pretty interesting game, Wario Land 3 is a cross between a platformer and a Metroidvania. Game's structured as a set of levels that you access through an overworld (like a traditional platformer), but each level features multiple exits, which unlock as you progress through the game. Each exit has a treasure chest which contain all sorts of items, from power-ups for Wario's moveset to random objects that unlock new levels or open pathways in levels that you already visited before. This structure creates a pretty fun loop where you're constantly revisiting "old" levels and finding new paths in them to unlock new stuff in the game.
Now, regarding the gameplay itself, WL3 is more of a regular platformer with a focus on puzzles but it has 2 interesting mechanics. First, Wario has no lifebar or anything of the sort, so you can't "die" like you do in any traditional platformer. Instead, the punishment of mistakes is mostly losing time as the game forces you to retry some sections of the level. Second, since enemy attacks don't "hurt" Wario, what they do instead is "transform" him, giving him new properties that hinder Wario but also allow him to access new parts of a level. For example, there's a zombie-ish enemy that transforms Wario into some sort of slime that falls through the floor. This enemy is usually put as an obstacle in vertical sections of levels, so when you transform into slime you'll fall down and be forced to climb up again. At the same time, however, there are sections of the game where you'll need to intentionally transform into slime Wario to fall through the floor and progress through the game. It's a pretty neat mechanic and the game features a fair amount of fun transformations.
Overall, this is a pretty enjoyable game with a very interesting design. However, I have to say that I mostly enjoyed it since I was playing it on NSO and, thus, had access to the "Rewind" feature. Otherwise, I'd have gotten extremely annoyed at how the game punishes you, since it mostly makes you waste time, especially on boss battles.
Now, regarding the gameplay itself, WL3 is more of a regular platformer with a focus on puzzles but it has 2 interesting mechanics. First, Wario has no lifebar or anything of the sort, so you can't "die" like you do in any traditional platformer. Instead, the punishment of mistakes is mostly losing time as the game forces you to retry some sections of the level. Second, since enemy attacks don't "hurt" Wario, what they do instead is "transform" him, giving him new properties that hinder Wario but also allow him to access new parts of a level. For example, there's a zombie-ish enemy that transforms Wario into some sort of slime that falls through the floor. This enemy is usually put as an obstacle in vertical sections of levels, so when you transform into slime you'll fall down and be forced to climb up again. At the same time, however, there are sections of the game where you'll need to intentionally transform into slime Wario to fall through the floor and progress through the game. It's a pretty neat mechanic and the game features a fair amount of fun transformations.
Overall, this is a pretty enjoyable game with a very interesting design. However, I have to say that I mostly enjoyed it since I was playing it on NSO and, thus, had access to the "Rewind" feature. Otherwise, I'd have gotten extremely annoyed at how the game punishes you, since it mostly makes you waste time, especially on boss battles.