Nebulus is a computer game created by John M. Phillips and published by Hewson Consultants in the late 1980s for various home computer systems. International releases and ports were known by various other names, including Castelian, Kyorochan Land, Subline and Tower Toppler. The player character, a small green creature called Pogo, is on a mission to destroy eight towers that have been built onto the sea, by planting bombs at the towers’ peaks. Pogo’s progress is hindered by enemies and obstacles, which he has to avoid in order to reach the top of the tower.