anyone remember this game?

Hi!
This one day I remembered a gam I played a looong time ago - on some 8-bit old-school game computer (the ones on which games like Mario or Battle City were played) - and the problem is - I can't remember the name of it. But I can tell you what it had in it - so you were like a digger - searching for crystals by digging through ground - and the ground changed its color from level to level. there were stones, which fell down when you dug the ground away below them and you had to look out for these - so that they don't crush you. also, there were thes funny color-changing rectangles - like psycodelic style and they were randomly running around and you had to watch out for them too. And the game(ie. level) was finished when you found and colected all of the crystals and went to the exit. Also, where can I get a emulator for this kind of old machines (and games as well)?