For me it was Terraria, Satisfactory, Tetris Effect Master Mode, Minecraft with Mekanism mod & CSGO / CS2 (almost 2000 hours in CS alone).
Edit: There are so many answers that I might only reply if I have something interesting to say. I will read all of your answers though. 🙂
Edit 2: It has become too much for me and I have to disable notifications. Thank you for the massive response and please continue to discuss with everyone here. ❤️ 🫡
I saw a lot of factory games in other comments but I didn’t see my drug of choice : Captain of Industry. The process chains are really complex and you can’t just throw space at a problem. I played for 24 hours straight once without getting up from my chair.