Tower Tier Zero, a tower-defense game set in the future on a world called Terra Zero, has faced a threat from a race known as [A]liens for thousands of years. The race uses special weapons known as [A]ngelus to attack the planet. The player's mission is to use TowER defense systems to protect human existence in the form of consciousness saved on computer servers. They must use various strategies and quick thinking to defend forested areas with open green spaces and rocky outcropping using main turrets and secondary support turrets.
During gameplay the player uses CR to purchase support turrets. Whether they perform well during the mission or not, they're rewarded UP and RP that they use to upgrade turrets and unlock turret perks, respectively. For example, they use RP to improve weapon reload speed. They can perform two upgrades and unlock three perks for any main turret. The player reviews turret stats to better understand these options, including stats for attacks, armor pierce, energy shield damage, rounds per second and magazine.
In Tower Tier Zero, the player improves their defense of an area against [A]ngelus by watching advertisements as well. They can receive 2x damage points or reload speed. They can also multiply their income.