Finished Hollow Knight: Silksong? Didn't find it punishing enough? You should really take a look at Stardust Demon. An overlooked gem with some pretty rad looking design, and a game that just keeps on expanding as you go through it. I was quite shocked to see it only had 67 user reviews on Steam.
What is it: Stardust Demon is a Cave Story-inspired metroidvania with an emphasis on its world's story and cute characters, and challenges that ramp up in difficulty including precision platforming elements. The aesthetic of the game uniquely combines colourful pixel-art with retro FMV cutscenes. Its eclectic soundtrack melds chip-tune, electronica, and metal influences together.
It originally released back in October 2024, and last month they added a major upgrade including a new Boss Rush game mode.

Direct Link
It has Native Linux support, and on Steam Deck it's rated Playable (need you to manually change resolution). If you can handle the difficulty, if you love a proper challenge - it's one not to be missed.
Game Highlights:
- Mixture of platforming, action, and puzzle gameplay.
- Exploring multiple planets.
- Weird and wonderful NPC's, rich and vibrant worlds.
- Shops and optional quests.
- Cutscenes with charming sprite animations.
- Puzzles with varied mechanics including teleporting, reversing time for specific platforms, and more.
- Many secrets and upgrades to be found.