Towers

There are nine towers in the game and two mega towers. These towers can be upgraded to LV4. Before you can upgrade a tower, you should spend collected Stars in the Lab to unlock various towers and their next upgrade level. For each upgrade, the cost and resell value of the tower also skyrockets. Unfortunately, only the damage of the towers are increased per upgrade; their firing rate and range stays the same.

EWTD2 allows players to spend collected "Stars" from missions to unlock new towers and upgrades. These upgrades are laid out in a straight line instead of a "skill tree" format; you must unlock the currently available upgrade before you can unlock the next one. There's also no point of farming Stars since you'll earn just enough to unlock stuff from the Lab as you progress. Replaying a mission doesn't earn you anything worthwhile so basically, every map is a forgettable affair.