Games are as much about what they don’t let you do as what they do. Figure and ground. The tools they withhold from you are often more important than the tools they provide. Constraint guides cleverness and creativity.
Supercell’s Clash of Clans is a fairly typical free-to-play mobile game on its surface. You build a town. It takes a while. You can pay money to make it take less of a while. You build troops, and they follow the same pattern. What’s a bit unusual is that you can rearrange your town, and the layout you choose matters. When a town is raided, the placement of its defenses means the difference between winning and losing. Especially because you can’t control your troops.