This is one of the best first person platformer/parkour games in the genre, with gameplay second only to Neon White, in my opinion. The presentation is minimalist and uninspiring, and the total number of gameplay elements is quite small, but that just makes the depth available even more impressive.
The movement system has a lot of specific nuances and idiosyncracies (like the lack of air control, the fact that you keep your speed when jumping off of walls, or crouch jumping) which you need to figure out and understand on your own, since the game doesn't teach you them very well, however each piece is deliberate and carefully considered to create a tight and expressive movement system with a great sense of speed and flow. The skill ceiling in this game is incredibly high, and you are expected to master this movement system, step by tiny step.
The level design is top-notch, levels will usually have many viable routes, and figuring out the best way through each one is very satisfying, as they often have tricks and skips you don't notice on your first run through. Being able to race against player ghosts is great for this, when you are struggling and need confirmation on what the perfect line actually is.
There's a map editor with steam workshop support and multiplayer, but the multiplayer, while still functional is absolutely dead, and I can't vouch for the quality of most community maps. Even without the extra content, I think the game is absolutely worth the price, and if it's on sale, even better.

This is a very hard game. You might look at the Steam page, see that it has 25 levels, and think "that's not a lot of content" but you can look at the 70 hours I have on record, and know that that is all only for getting all gold medals (which isn't even the highest tier), and all spheres (secondary collectables hidden around on each level). The level of precision and consistency which is asked of you, sometimes just for finishing a level cleanly, let alone getting a gold or platinum time, is often at the level of difficulty I would expect from hidden/post-game completionist content in any other speedrunning game (green medals in Trackmania, red medals in Neon White), especially as you push into the last 10 levels. This is not inherently a problem, if you're willing to bash your head against the levels and develop a proper mastery, but this is not really a game where you can muddle through with slow times and a mediocre understanding of the mechanics and still have a good time. Most of the content here is at a level where you need to really master it to engage with it properly, and if you aren't willing to make that commitment, you probably are either going to get really frustrated, or just not make it through the whole game.
I can tell you that I made the commitment, and I found it incredibly worthwhile, but you have to figure out your own threshold for acceptable difficulty.

This is one of the best first person platformer/parkour games in the genre, with gameplay second only to Neon White, in my opinion. The presentation is minimalist and uninspiring, and the total number of gameplay elements is quite small, but that just makes the depth available even more impressive. The movement system has a lot of specific nuances and idiosyncracies (like the lack of air control, the fact that you keep your speed when jumping off of walls, or crouch jumping) which you need to figure out and understand on your own, since the game doesn't teach you them very well, however each piece is deliberate and carefully considered to create a tight and expressive movement system with a great sense of speed and flow. The skill ceiling in this game is incredibly high, and you are expected to master this movement system, step by tiny step. The level design is top-notch, levels will usually have many viable routes, and figuring out the best way through each one is very satisfying, as they often have tricks and skips you don't notice on your first run through. Being able to race against player ghosts is great for this, when you are struggling and need confirmation on what the perfect line actually is. There's a map editor with steam workshop support and multiplayer, but the multiplayer, while still functional is absolutely dead, and I can't vouch for the quality of most community maps. Even without the extra content, I think the game is absolutely worth the price, and if it's on sale, even better. This is a very hard game. You might look at the Steam page, see that it has 25 levels, and think "that's not a lot of content" but you can look at the 70 hours I have on record, and know that that is all only for getting all gold medals (which isn't even the highest tier), and all spheres (secondary collectables hidden around on each level). The level of precision and consistency which is asked of you, sometimes just for finishing a level cleanly, let alone getting a gold or platinum time, is often at the level of difficulty I would expect from hidden/post-game completionist content in any other speedrunning game (green medals in Trackmania, red medals in Neon White), especially as you push into the last 10 levels. This is not inherently a problem, if you're willing to bash your head against the levels and develop a proper mastery, but this is not really a game where you can muddle through with slow times and a mediocre understanding of the mechanics and still have a good time. Most of the content here is at a level where you need to really master it to engage with it properly, and if you aren't willing to make that commitment, you probably are either going to get really frustrated, or just not make it through the whole game. I can tell you that I made the commitment, and I found it incredibly worthwhile, but you have to figure out your own threshold for acceptable difficulty.