The game references both Robbo from Atari and the first part of Amirobbo, which some people don't like. The first 10 levels feature levels and refined graphics from Robbo from Atari XL. The next 10 levels are levels from the first part of Amirobbo along with graphics of that game. Only from the 21st level do the “new worlds” begin. I'm glad you like the game. I wish you a lot of fun :)