How many bricks can the game support before hitting memory issues? I'm guessing all the bricks have combined meshes
The game is no where close to being optimized, so I think it's a bit early to answer that. Last I checked, I was able to get 2,500 bricks on screen at once with hardly any issues. But, will do more extensive stress tests once more optimization techniques are added.
Eventually, I should be able to get the brick system to be very close, if not, exactly as efficient as Blockland handles it. Right now, yes bricks are combined into a single mesh. But, later on I'll add adjacent brick face occlusion, make some changes to the brick mesh handler / octrees to take full advantage of frustum culling, implement occlusion culling (i.e. hiding bricks behind other bricks - once I buy the full version of Unity), and possibly add other techniques like distance culling. You'll also have the option to toggle shader options, as an additional way to improve the game's performance.