This was a great minimalist lo-fi puzzle platformer that is somewhat held back by a few issues with UI and design.
I liked the great mix of platforming and puzzling. A great example of this was the ability to use the speer to climb walls. It was consistently delightful, and felt entirely satisfying throughout the run. I also liked that the speer had a small throwing arc, and this was even relevant in a few levels. Finally, levels are plentiful and varied, while still being rather quick to complete.
I did have a few issues with the UI in particular, though I feel like these could easily be fixed. First of all, both speer-throwing (which pushes stuff away) and grabbing, i.e. two opposing actions, are on the same context-sensitive button. This led to a lot of feelsbad moments for me. I had to restart so many levels because I accidentally shot something I'd intended to grab. This either destroyed it, or pushed it away - often into spikes.
Secondly, it's too easy to drop items on a controller. You're supposed to drop them with Down on the D-Pad, but they also often got dropped when I used the analog stick and dipped slightly below the horizontal line, i.e. when the analog stick sent a Down signal (maybe this was a bug?). I found a workaround by always keeping the stick in the upper half, but it was pretty irritating.
Thirdly, there's an "Annoyed?" level skip prompt. I very much appreciate the intent behind this feature, but the implementation had an unfortunate UI: upon death, it pops up without delay, and the button prompt defaults to "yes". I frequently died while pressing X to throw speers, at some point the Annoyed prompt popped up, and so I accidentally skipped to the next level. So the "Annoyed?" prompt became a self-fulfilling prophecy.
In terms of the design, I wasn't a fan of the power gems. I often had to reset levels because I accidentally broke such a gem at the wrong time, or because I shot a power speer a few pixels too low or too high. I wish the dev had found a design that allowed these gems to respawn (without trivialising the puzzles).
The timed speer obstacle was another cause of frustration. And finally, it was weird that you couldn't drop down, then move sideways into a niche 1 tile high. I don't mind that as a standalone design, but it runs counter to most platformers, and in this game there was no visual indication that anything would be different.
Finally, a design I was ambivalent about: A few of the levels in the later stages aren't tightly designed, i.e. you can collect the emblem (= 100% the level) without using all the gems and items. I didn't exactly mind, since I'd gotten somewhat exhausted by that point. But I expect this wasn't intentional.
Ultimately, I liked Speer, and without these few UI issues, I think I might have loved it. It's polished and enjoyable enough that I'm surprised it wasn't released on Steam.