I say get Minecraft, it's like 30 bucks now, and I swear, i've dumped over 1,000 hours into this game. I use it to relax. You could play on peaceful if you want, but it's really not that bad on easy or normal if you want a mild challenge. The multiplayer is really quite good, with economy mods, a mod that lets you level up skills like mining, herbalism and whatnot. Or you could go the casual adventure map route, and some of them provide some pretty interesting stories and mechanics. If you don't care for the retro look, you can get texturepacks that make it look however you like, or make your own it you're picky. If you don't feel like playing on servers, then you still have more than enough mods to suit yourself once you get bored with normal mode. This game is about doing anything.