I don't know if this was just my copy or a known bug, but I recall when I played it, on the last tower, the game simply froze when you enter the exit door. Was it supposed to end like that or is that a bug?
Also, this could be my mind playing tricks on me, but I thought I recalled seeing screenshots of the under water parts (between the towers) for the CPC version, but on my game those parts never existed as far as I know.
edit: My copy was the Amstrad Action cover tape
Unfortunately, this is a very well known bug with the original tape/disc versions.
However, Kukulcan & CNG have fixed versions of the original and trained cracks here (http://www.cpc-power.com/index.php?page=detail&num=1499)!
Quote from: blackdalek on 15:19, 19 November 17
Also, this could be my mind playing tricks on me, but I thought I recalled seeing screenshots of the under water parts (between the towers) for the CPC version, but on my game those parts never existed as far as I know.
From what I understand, Nebulus was only released on the Spectrum, Commodore and Amstrad 8bits initially, although in the US, it got released on the NES and Atari 7800 as 'Tower Toppler' later. 16bits also got a release around the same time as the 8bits, but that's beyond the scope of the discussion.
Back to my point. Out of the 3 initial 8bit outings. Only the C64 had the bonus level. The Amstrad didn't see it (despite the fact that the loading screen derives from the bonus round!), and the Spectrum was never going to see it as the game came out before the 128k machines surfaced, and there's only so much you can do with 48k.