Recommend me a game

Hi all,

Recommend me a game! I'm looking for something casual (to play for 20-30 minutes from time to time), challenging (like in difficult to master), not super complicated (I don't want to spend hours learning all the rules), but not super simple (when it's too repetitive the patters get ingrained in my brain. anyone else has this?), cheap (don't want to spend $30 on a game I will play from time to time). Must work on Linux and on an integrated GPU. Games I enjoyed previously:

• Fistful of Frags
• smashcarts.io
• xevil

What I did a lot years ago was to play single levels of games over and over until I totally crashed it even if I wasn't that interested in the entire game. I guess what I like most is figuring out the smallest details of a game, not getting into long campaigns.

So, what can I play?

Edit: Thanks for all recommendations so far but I see I need to add one more requirement: no levels. I'm looking for something quick, in and out, skirmish, death match, melee type of game. Not something where you build a character, solve puzzles and so on.