In games with linear progression, levels are areas of a larger world. Games may also feature interconnected levels, representing locations. Although the challenge in a game is often to defeat some sort of character, levels are sometimes designed with a movement challenge, such as a jumping puzzle, a form of obstacle course. Players must judge the distance between platforms or ledges and safely jump between them to reach the next area. These puzzles can slow the momentum down for players of fast action games; the first Half-Life's penultimate chapter, "Interloper", featured multiple moving platforms high in the air with enemies firing at the player from all sides.
Level design or environment design is a discipline of game development involving creation of video game levels—locales, stages, or missions. This is commonly done using a level editor, a game development software designed for building levels; however, some games feature built-in level editing tools. Level design is both an artistic and technical process.
A bonus stage (also known as a bonus level or bonus round) is a special level within a video game designed to reward the player or players, and typically allows the player to collect extra points or power-ups. Bonus stage either have no enemies or hazards, or replace the normal penalties for being struck by enemies or hazards with simply being thrown out of the bonus stage. Many bonus stages need to be activated or discovered in some manner, or certain conditions must be satisfied to access them. Otherwise, they appear after the player has completed a certain number of regular stages.