Diep.io

Diep.io is a 2D MMO game similar to Agar.io. The player controls a simple tank and shoots powerful Bullets, Drones, or Traps at Polygons and other tanks to level up and upgrade their tank to the next level.

Game Modes
There are a variety of game modes to suit one’s style of play. Free For All or Maze are fun options for solo tanks. For those who wants the “Last Man Standing” gameplay, Survival is there. If one wants to join friends and destroy the enemy, 2 Teams or 4 Teams is suitable. For capture and control of ridiculously powerful tanks, one may choose Domination. A player can convert other players to their team in Tag. If one wants to play around with tank classes, there is the Sandbox. In total, there are a total of 8 available game modes to play: Free For All, Survival, 2 Teams, 4 Teams, Domination, Tag Mode, Maze, and Sandbox.

Controls
Although all one really needs to play the game is WASD (or the arrow keys) to move and click to shoot, there are many other controls in this game. W or [↑] for up, A or [←] for left, S or [↓] for down, D or [→] for right.
 * Movement: WASD or [↑ → ↓ ←]
 * Aiming: Mouse - the tank will point toward the player's mouse.
 * Shooting: Left click, or press space. Hold works too if clicking many times is disliked. One can press “E” for Auto Fire.
 * Drone Repel: Right click or Shift - drones from the Overseer, Overlord, Manager, and Necromancer will move away from the mouse.
 * Upgrade: Either click the “+” button next to the stat one wants to upgrade with the cursor or press the number key shown next to the upgrade stat.
 * Auto Fire: Press E to turn on Auto Fire - the tank will shoot continuously without the need to hold the mouse down. Press E again to turn Auto Fire off.
 * Maximize Stat: Holding M and a number key will automatically place upgrade points as they become available into the stat corresponding to the number. Pressing M alone will cancel maximization.
 * Auto Spin: Press C to turn on Auto Spin - the tank will spin slowly, no matter what one's mouse is doing. Press C again to turn Auto Spin off.
 * Full screen: Press F2.
 * Open class tree: Hold Y to show the entire class tree (all the classes, and the path to get them). After one finishes looking at it, they may release the Y key to avoid lag.
 * Take control of Dominator: After the player’s team has captured the Dominator, they can press H to take control of it (without spamming it). The controls stay the same, except one cannot move.
 * Releasing control of Dominator: Press H to release control. If the player spams the H button wanting to take control of the Dominator, they will end up killing themselves and not taking control of the tank.

Classes
Diep.io also features a huge variety of playable classes, which can be upgraded at levels 15, 30, and 45

(max level). One starts as a normal Tank with a single Barrel which shoots a single Bullet and begin to work your way up from there. Every 15 levels, they may choose to step up to the next available Tier, which is an organization of classes. Tiers, in turn, are sorted in the class tree, shown on the right.

Below is an expanded table of tanks, sorted by Tier and by availability:

Stats
When one levels up, they also gain points that you can put towards upgrading the stats of their tank, which boosts certain characteristics: After every level up through 2-28 the player gets an upgrade point to upgrade one of those stats from a menu like the one seen here. Then, every 3 levels from 30-45 they get an upgrade point.
 * Health Regen - Allows one to regenerate health faster
 * Max Health - Increases the amount of health one has
 * Body Damage - Increases the damage done by body collisions
 * Bullet Speed - Increases the ammunition velocity
 * Bullet Penetration - Increases bullet health and hence its penetration
 * Bullet Damage - Increases the damage done by ammunition
 * Reload - Increases one's rate of fire
 * Movement Speed - Increases the tank's speed of movement

Bosses
In Diep.io, as well as opponents, the player has the ability to fight powerful, AI-controlled bosses every 10-23 minutes the server is online. They will grant one loads of experience (30,000, enough to get a level 1 tank beyond the required exp needed for level 45) for the assailant. To be fair to new users, bosses will not target players under level 15 unless provoked. There are a total of 5 different bosses to battle:

Achievements
Achievements are rewards in Diep.io. One can obtain them through reaching specific requirements, shown on the achievement; some are harder than others, while some are extremely easy. There are 50 achievements in the game as of March 4th 2017. The player can see all achievements, with earned ones in color, by moving their mouse to the right side of the screen.

Trivia
       pt-br:
 * Many believe that .io is a game tag for multiplayer games. It is actually a domain in the British Indian Ocean Territory, where the British and the Chagossians take some of the profit from the people who use the .io domain. Since there are no Chagossians living in the area, and the British soon denied the profits from the domain, .io is a free domain.
 * Each server can harbor a maximum of 80 players (not including AI).