The core gameplay is great, really love it, easy to play but tough to master, near perfect in my opinion. My criticisms with the game mostly relate to UX issues.
Collectibles
Collectibles are supposed to motivate the user to behave in a certain way, but aside ticking boxes there's no incentive to collect these. Aside the 3 prisms, they're not tied to progression, and the player is given no clear incentive to pursue coins and blue circles. There's very little driving the player forward, in other games these collectible systems either relate to unlocking the next level, or unlocking gameplay and cosmetic upgrades. It's a shame that they don't feed into anything like that, I know that there's something to unlock at the end of the game, but that's an incentive that most players will never benefit from, and it does little to encourage you to persist to the end of the current level.
Tutorialing
Near non-existant, many users even on GAF have posted how they've basically hit a wall to their progression because they just don't 'get' the games mechanics. The game leads people in with its initial, easy level, but difficulty ramps up quickly without offering much guidance.
Having a hub world, or worlds connecting Snakes disjointed environments might have been a nice means of allowing players to experiment and learn in a safe, non-commital environment. This would have been a good means of retaining the games hands-off approach to tutorialing, while providing a more gradual introduciton to the games mechanics, facilitating an extended, organic opportunity to learn, before players are likely to hit any of the games more difficult segments.
Checkpointing
Some of the essential components of the levels are very difficult and but this in itself isn't too problematic, yet the checkpointing is. Having to repeat an incredibly difficult segment of the game because it wasn't followed by a checkpoint becomes tedious over time, and as does having to repeat less-difficult segments of the levels, because Noodles movement is slow and maticulous, it's really ardeous to repeat these segments over and over. You're not Super Mario or Sonic, you can't just zip over to the location of your last death, just getting from A to B is slow, and potentially challenging, and understandably not something players may want to repeat. Additionally, because of how checkpoints work players will likely find themselves returnng to previous checkpoints to effectively bank their progress in the level, before continuing onwards. This can be a tedious process. It doesn't add difficulty, and asks the player to spend more time back-tracking to register these checkpoints.
The game has plentiful difficulty for players that want it, and surmounting the games challenging obsticles feels difficult enough in and of itself, without asking players to repeat these segments. Similar to games like Trials and Trackmania (also complex, physics based games) reset players to just before they fail so that they may try again, allows the game to give all players a sense of progression, regardless of skill level, and avoid any repetition that some players may want to avoid. At the same time you can still incentivise perfect level clears, with additional medals and reward that recognise players have beaten the levels without resetting.
All or nothing
Levels are simply too long, and you can't quit and resume with your progress in tact. Players are likely to have an incredible amount of variance between their completion times for any one level, and it's easy to see how someone might spend an hour on a single level if collecting everything while struggling with the games difficulty.
You should be able to hop in and out of the games levels, completing them bit by bit. Games like Banjo Kazooie and Super Mario Sunshine actually have very intelligently designed progressional structures as they allow players to hop into a level for a brief period of time, make a contribution to their progression and then leave. I think I'm pretty decent at Snake Pass, at the time of writing this I actually have the world record time on the first time trial, yet I still feel like I spent a good 30 minutes or more on some of the games levels, repeating the more difficult segments due to difficulty, and scouring the level head to toe to find the collectibles. At times I felt fatigued, wanting to quit and do something different, but knowing I couldn't because the game doesn't retain my progress.
Camera and controls
There are no good alternative control options for players looking to customise the experience. I modified the controls using the PS4s accessibility features, and by using L1 to control noodle, and R1 to lift the snakes head. That frees up my thumb to control the camera at all times, which is better, but still, the camera isn't ideal. Perhaps some transparency would be nice, as I often feel that elements of the structure I'm climbing, or even noodle himself get in the way of what I want to see.
Menu
The games interface is aesthetically appealing but doesn't really contextualise the journey you're going through very well. It doesn't paint a good picture of the players progression in the same way that map-based level selection menus do (see Super Mario World, or Rayman Origins). At the same time, it's quite slow to scroll through and not immediately evident that you can press up to skip to the levels in the next world.
I really like Snake Pass but it would have been a considerably better game, having been likey to have experienced a considerably better reception, if it had paid more consideration to the user experience. Features like a hub may seem like a considerable body of extra work, but it would have gone a long way towards allowing players to experiment without consequence, while reworking the checkpoint system and making the levels more bitesized by allowing players to jump out when they pleased, would have enabled even the games more challenging content to appear more approachable.