Created this map in a few hours. It's a fun little minigame of defense. You can train units from the factories and they spawn in the battlefield. There are a range of terran units from the marine to the thor. You can get the upgrades from the Dark Shrine, which you are trying to protect. If the Dark Shrine dies, you lose the game. It may get difficult pretty fast, the increase in enemy spawn is something that I am still working on. I hope you have fun!
(the vehicle upgrades do upgrade the Viking)
Thanks to Frossen for helping me with triggers and giving me ideas for new versions.