So long as the player isn't under attack, their health will regenerate fairly quickly, eliminating the need to replenish health between missions. Enemies in any given mission will usually be within the player's ability to defeat, though it is possible to be overwhelmed by sheer force of numbers. In terms of difficulty, a solo player can progress in the game without much trouble. Once activated, Nanos will aid the player until they are put away or tire out, at which point they will vanish in order to regain their strength.New nanos include Mordecai, Rigby, the Sym-Bionic Titan, and as usual, Ben 10 aliens. Players are limited to carrying three Nanos at a time, which can be switched out at Nano stations. Nanos grant a wide range of abilities depending on the specific Nano, ranging from increasing the player's performance (run speed, jump height, etc.) to special attacks (stunning moves, area-effect damage, etc.), as well as a number of player-cooperative abilities in the same vein. Once obtained, players can choose between one of three abilities for the Nano the chosen ability can be changed later for a fee. A Nano is granted to the player upon the doppelganger's defeat. Nanos are obtained during Nano missions, in which the player must defeat an evil Fusion doppelganger of a Cartoon Network character. The player's level was tied to the number of Nanos they have collected but had changed since before the last updates. The key to progressing in the game is the collection of Nanos, over 40 miniaturized versions of Cartoon Network characters which serve as allies in combat. Unlike the first two types of missions, which can only be done one at a time, the player can run four different World missions concurrently. World missions are generic tasks which offer lesser rewards, but are far more numerous to compensate. Guide missions are special tasks done on the behalf of the guide character, typically offering the best equipment available as a reward. A meter encircling the mini map called the fusion matter meter shows the player's progress in this regard. Nano missions are granted automatically once the player gathers enough fusion matter but now you get the mission from the character fought or gotten. Missions come in three types: Nano missions, Guide missions, and World missions. Missions are given by various Cartoon Network characters around the game world, who usually cluster around travel hubs. The main focus of the game is the completion of missions.
The player can switch between guides if they choose at a guide changer. After leaving the first level, they can choose between four guides: Ben Tennyson, Edd ,Mojo Jojo, and Dexter. The player is guided in their quest by a specific character, beginning with Dexter's computer, Computress. Instead, they gather a loose analog known as fusion matter (which has multiple purposes) through defeating enemies and completing missions, and upon collecting enough can perform a mission to raise their level, but as of February 16, fusion matter acts more like experience as players can now perform multiple nano missions every four levels.
Unlike ordinary role play games, the player does not gain experience in the conventional sense. The player is provided with various weapons to accomplish this, including ranged and melee weapons. Gameplay primarily focuses on accomplishing missions. The game has large playable environments, with travel facilitated by various warp points. Their character is viewed from a third person perspective, viewing the HUD, and the range of movement consists of walking in any direction and a short-distance jump.
In Fusionfall, the player takes control of a customized avatar.