Terraria is pretty fun! :) It's open-world. When you first start the game, you can generate a map that's either small, medium, or large -- I'd recommend the large -- and then it's up to you to explore the land, the underground, and even the skies.

There are bosses to defeat, but you do them at your own pace, and for the most part you summon them yourself when you're ready. As you get stronger and find more health and magic, stronger random events happen to match your strength but there are still the normal things too.

Once you defeat a certain boss though, it transforms your world into a harder world with new mobs and challenges entirely.

It's great! :D

I play it on PC, but it's available on Android and the Switch as well. Probably a few other things.