Tiny Thor is an enjoyable, though not particularly amazing, platformer. Though the good outweighs the bad, this is not a game without some issues.
To begin with, the art and music are both great and work well alongside the lighthearted tone and often fast-paced action platforming of the game. Unfortunately, the high quality is undercut by just how little variety there is. This is especially true of the third region since, while it has about as many levels as the previous two regions, its levels tend to be much, much longer and by the end I was well and truly tired of listening to the same music alongside the same icy mountains and frozen temples.
Platforming generally feels good and Thor has a versatile moveset which allows for some complicated maneuvers. Between walljumping, a double jump, and an air dash, Thor can cover a lot of distance before touching the ground and the later parts of the game will often require you to string these skills together in one way or another while under pressure from enemies or environmental hazards. Thor sometimes spends so much time without touching the ground that it can become easy to lose track of if you still have a jump and/or a dash remaining so it would have been nice to have a visual or auditory cue tied to those, but I otherwise have no issues with the standard platforming in this game.
However, one thing I certainly have a few problems with in Tiny Thor is the hammer. The hammer rarely feels good to use, which is a rather large problem when it's one of the game's defining features. Thor is able to aim his hammer before throwing it and the hammer will bounce off of not just physical walls, but also the edge of the screen itself. Many of the more puzzle-focused challenges in the game require you to bounce the hammer at a certain angle or to trap the hammer somehow to make it rapidly bounce in a smaller area. Aiming the hammer can feel finicky, especially if you're on moving or breaking platforms, and this is compounded by the hammer's hitbox being smaller than its sprite implies - even by the end of the game I frequently missed hitting various objects by a handful of pixels.
Bouncing the hammer off of the screen itself sounds like an interesting idea, but it mostly ends up feeling weird and needing to make use of the screen's edge rather than static environmental objects often left me wondering if I had actually figured out the intended solution to the various puzzle-platforming challenges or if I had found a significantly more awkward solution the developers didn't plan for.
The last issue with the hammer is you'll often want to set it to bounce in a straight vertical or horizontal line, but Thor will immediately catch the hammer if he touches it (often resulting in death for one reason or another), which means you often need to awkwardly make sure you have enough space to throw the hammer and then get completely out of its way before it rebounds. Pressing the hammer button while the hammer is out will make the hammer zoom back to Thor, so making Thor automatically catch the hammer on touch feels completely unnecessary and only gets in the way.
There are a few other oddities worth noting as well. For example, blue gems are Tiny Thor's version of currency and, like coins in most platformers, strings of gems are often used to guide the player along platforming paths, especially when the destination is not initially visible. However, gems collected in a run of a level remain gone after dying and respawning, depriving the player of a useful visual indicator, which is an especially odd choice since ghost versions of the gems *do* appear if you replay a level. Tiny Thor has some issues with its visual language too, such as the hitbox on horizontal bounce mushrooms being much smaller than the whole mushroom, the ice covered walls (which you can't jump off of) sometimes blending in a little too closely with the heavily snow-covered walls (which you can jump off of), and the fact that any enemy not covered in spikes is safe to jump on - except for the very round ghosts, which will kill you.
Even with its various issues, I think Tiny Thor's level design is quite solid overall. It presents a good challenge and the difficulty curve was pretty stable; Tiny Thor is a hard game without being overly demanding and the only frustration I ever felt was from some particularly awkward hammer-throwing moments. Checkpoints are frequent and generally felt properly distributed. There were a few moments in the later parts of the game where I died because I didn't know what to expect from a new room, but these were also consistently within ~5-10 seconds of a checkpoint and with infinite lives it hardly mattered. Most of the boss fights were also entertaining and level mechanics were generally varied (floating on wind currents got a bit old).
Tiny Thor has its share of issues and rough edges, some more severe than others, yet it often provides a solid, enjoyable platforming experience. While this certainly isn't the strongest recommendation I've given to a game, I don't regret my time playing Tiny Thor and I think it's a game worth considering for anyone looking for a challenging platformer.