Depending on what you mean by casual, I consider Dead Cells a casual game, because whenever I'm bored I pick it up and play for a while, but it's one of the hardest games I've played, however because it's rogue like it doesn't matter if you die a lot. Another similar example would be Factorio with enemies turned off, just go there, fix something, add something new and quit the game near the next thing you want to do so you remember it next time.
If you're looking for a more traditional definition of casual games I tend to play those in the phone, I really like mini metro and super hexagon (although again, this one might not fit your definition of casual)