The 2D Battle Simulator is the best way to simulate a real-time strategy game. It lets you play through 100+ campaign levels, as well as the zombie mode, where you can get as far as you can from your base. And if you just want to play around in the sandbox, you can do that, too.

The campaign mode has a number of different levels, where you have to simulate a battle for the first place. You can play with a number of different units from the various faction tabs. Each unit has its own characteristics, such as its strength, health, etc.