Tiers

 are separate Tank Classes, organized with the characteristics of their Cannon(s).

Tiers are represented in the Class Tree, shown on the picture nearby, as a series of concentric rings containing every tank in the game. It can be displayed in-game by holding the Y key. In the direct center of the Class Tree is the starting tank, or Tier 1, or Level 1. The first ring contains Tier 2 (Level 15) tanks, the second ring contains Tier 3 (Level 30) tanks, and the outermost ring contains Tier 4 (Level 45) tanks. Areas shaded black on the tree indicate an unavailable Upgrade in that tier. For example: You have to press ignore once from the basic to get to the Smasher

There is a recurring pattern of colors in the upgrade selection menu and the Class Tree. The first tank will always have a light blue background. The second tank will be green. The third tank will be red. The fourth tank will be yellow. The fifth will be dark blue. This is only used for Battleship, Smasher and Auto Trapper. The sixth option will be purple. The Factory is the only tank so far with this color. The color order can be found in the tank’s Stat buttons which are color-reversed. The game mode selection buttons and colored Achievements list also use that pattern. Regardless of speculation, these colors do not seem to represent anything other than a simple order pattern to more easily distinguish tanks apart when quickly selecting an upgrade for now.

Tier 2: Level 15
Upon reaching Level 15, the player may choose to upgrade to one of these Tier 2 specializations, or ignore them to get to the Smasher.

Tier 3: Level 30
Upon reaching Level 30, you may choose to upgrade to one of these Tier 3 specializations:

Tank Upgrades
Note: This requires players to stay as a Basic Tank until at least Level 30.

Tier 4: Level 45
Upon reaching Level 45, the player may select one of these Tier 4 specializations. This is the final tier that most tanks are able to legitimately reach and is also the final level that any player can reach, unless they press H in Domination game mode to become the Dominator which is fixed at Level 75.

Machine Gun Upgrades
Note: This requires players to stay as a Machine Gun until Level 45.

Removed Upgrades
These Classes existed at one point in the game, but have since been replaced or removed altogether.

Other Upgrades
These are classes that used to be in a different Tier, had a different design, or used to work differently but were kept around and tweaked.

Special
These do not branch off anything; they are only obtainable in Sandbox apart from Developer which is only used by the Developer, Zeach himself. The Dominator is the only tank which can be obtained in another game mode by any player by pressing H; that game mode being Domination.

Trivia

 * All Tier 4 tanks are 126-175 pixels wide.
 * If there were to be a seventh tank from a branch, the background color would be pink, as shown by the Game Mode selection, the colored Achievements list and the reversed Stats colors. For an eighth, it would be tan . It is unknown what a ninth tank would be, but since the colors used by the achievements list cycle through the eight colors, it would most likely be light blue.
 * There was a running theory that the background color of the Upgrade icon corresponds to the base Stat debuff it gets, as it typically matches the color of the respective Stat bar.
 * There are several issues with this:
 * If the background color were to depend on the tank’s Stat debuff, there wouldn’t be color variants, as seen in the Overtrapper, Auto Gunner, Streamliner, and Battleship, for example.
 * The Stat debuffs aren’t necessarily true: For instance, the Battleship may have a dark blue background, but with its notoriously fast Drones, it certainly doesn’t get a debuff to the Bullet/Drone Speed.
 * In general, the theory can be debunked with simple Sandbox testing.
 * Most of the fully removed tanks had a light blue upgrade background. The only removed tank with a different background color was the Auto 4.
 * These Stats are not changed upon upgrading to every tank (which means no buff or debuff): Health Regeneration, Movement Speed, Max Health.