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. Often a bonus stage will have no enemies or hazards, or may contain them but the player character is invulnerable to attack from them and cannot be harmed. Some games have bonus stages where the player character can be harmed by enemies or hazards, but will not lose health or lives if killed. Many bonus stages need to be activated or discovered in some manner, or certain conditions must be satisfied to access them, making them secret levels. Some games also contain bonus stages that are not secret but are compulsory and must be played, often at the end of the regular stages. They are often much shorter than regular stages.