Elf Tree Defense

The elves have long been living in the sacred tree in a secret location far away from any form of civilization. They are peaceful creatures, but now that the minions have expanded they want to cut down many of the trees to build houses and outposts for their army. Luckily you are on the elves side in this defense game and they are heavily armed. You should command the elf troops and make sure that the tree remains forever green after these battles. Summon units and upgrade them in order to keep the enemy troops still while you shoot them with the huge crossbow at the same time.