Hey thanks for playing! I'm glad you enjoyed the generated boards/dungeons, that was probably the trickiest part to implement!
Unfortunately I didn't have time to add a proper tutorial but I'll keep that in mind for if I keep working on this game :) To put it briefly, revealing squares gives you resources to spawn more units as well as visibility (obviously) so you can tell if there's any threats or treasure there to plan accordingly.
I'm trying to subtly encourage players to use the TNT to reveal squares as it's cheaper than the resources you get from revealing said square and keeps your grunts out of danger (in case there's a zombie swarm hiding behind said square) but perhaps I should provide a stronger incentive...
Thanks for the playing the game and thanks for the feedback! :D