With Terraria finally being released to Android devices, I promptly joined the legions (but not quite as legion as Minecraft) of fans converted by its simple but compelling game mechanics (although art style is also a clear winner). These are:
1) to explore the world, you have to figure out new strategies and item combinations that will get you to through different biomes, mobs and bosses.
2) to craft new items you have to get more raw materials
3) to discover new types of craftable items you have to discover new types of materials (both item and raw material types open up new craft-trees) by exploring the world. This leads you back to 1).
Because finding raw materials is based on random rewards, it’s incredibly addictive. But as you have to try and figure out different strategies, it’s not just lever pushing and hence gameplay is engaging and creative. For fans of rogue-like games like myself – Terraria items are incredibly cool and as you never have enough material to craft it immediately, you’re always having to venture into dangerous territory.
Plus there are some mini-games which are fun in and of themselves: a doll-house build/decorate for your NPCs, a simple tower-defence using drop-pits, arrow-traps, lava, boulder falls etc and of course figuring out the best way to farming various renewable resources.
And this is only the solo-player version.