DD node - connect the dots in one line, if you succeed you will be challenges with harder and harder levels
Insights from the gaming industry
FPS Level Design
First-person shooters may be structurally composed of levels, or use the technique of a continuous narrative in which the game never leaves the first-person perspective. Others feature large sandbox environments, which are not divided into levels and can be explored freely. In first-person shooters, protagonists interact with the environment to varying degrees, from basics such as using doors, to problem solving puzzles based on a variety of interactive objects. In some games, the player can damage the environment, also to varying degrees: one common device is the use of barrels containing explosive material which the player can shoot, destroying them and harming nearby enemies. Other games feature environments which are extensively destructible, allowing for additional visual effects. The game world will often make use of science fiction, historic (particularly World War II) or modern military themes, with such antagonists as aliens, monsters, terrorists and soldiers of various types. Games feature multiple difficulty settings; in harder modes, enemies are tougher, more aggressive and do more damage, and power-ups are limited. In easier modes, the player can succeed through reaction times alone; on more difficult settings, it is often necessary to memorize the levels through trial and error.