An open world platformer where you express yourself with different movements, Demon Tides looks like a lot of fun and it just had a huge demo upgrade. It's in development by Fabraz. A name perhaps you might recognise from Slime-san and Demon Turf.
You navigate the open seas to find distant structures, which you then explore with a diverse set of moves. Beat challenges, find chests and go collecting. Some trinkets you find can even modify and expand you abilities and outfits. Looks really cool, check out the original reveal trailer:

Direct Link
A big 2.0 demo update just went live that includes a whole lot of performance improvements, especially nice for devices like the Steam Deck. It's a long list of what's changed, including lots of gameplay updates and bug fixes. Well worth a go now and should work fine with Proton.
Game Highlights:
- A deeply expressive platforming move-set that enables you to travel through the world in countless unique ways. Express yourself through your schmovement and get lost in the flow!
- Travel the seamless, open ocean and reach any point of interest at blazing speeds! Explore each locale and figure out creative ways to beat challenges or reach certain areas!
- Hang out on your mobile hub, the Floating Fashionista, to chill with your crew or buy new items of interest!
- Discover hidden secrets and use context clues to unravel this world’s mysteries alongside the main story told through major, cinematic story events!
- Place your own checkpoints wherever you want and return to them any time you meet your untimely demise.
- Collect over 50 unique talismans that uniquely modify or add to your move-set! Get a paraglider to soar the skies, spawn a bubble to float in place indefinitely, change your spin form into a hookshot and so much more!
- Acquire a ton of unique head gear, outfits and hair dyes to change up your appearance! With over 50,000 possible combinations there’s no shortage of drip.
- Compete for the best completion times of each locale by racing other player's ghosts! Get notified if your ghost was beaten to challenge them right back, may the best runner win!
- Create and share graffiti that will appear in other player’s worlds! Make something pretty, hint towards a secret nearby or troll the players with lies you little rascal!