Today I learnt that BBC kids had a weird knock-off of Boulder Dash called Repton instead of a weird knock-off of Defender called Repton. :)
(Wikipedia claims that Beeb Repton was built entirely on the description of Boulder Dash found in a review, rather than actually playing Boulder Dash.)
This is going back a fair few years now, but having played both, my recollection is that Repton is a bit of a different game. The diamonds in are always stationary, and everything else runs in lock step, so there's no chance of outrunning the rocks or the scrolling.
(Wikipedia claims that Beeb Repton was built entirely on the description of Boulder Dash found in a review, rather than actually playing Boulder Dash.)