Diamond Adventure sets itself up in the manner of a graphical adventure game, but I think it is more similar to a puzzle game. You play the role of a thief and you have to steal loot, presumably a diamond. To do it, you have to remain undetected, avoid traps, find items, etc. As far as I can tell, the whole adventure takes place in a single apartment building.

As is stated on the box, this game requires dB BASIC. I am not sure why some games were written for this language. I think from a financial perspective, it doesn't make much sense. dB BASIC was a third-party purchase for the consumer, and I doubt half the X1 user base had it, while X1 came with Sharp's own X1 BASIC, so essentially every X1 user had it. To be sure, not *many* games were written for dB BASIC, and one of the couple of games I've run into that require dB BASIC was actually coupled with dB BASIC, so that one makes sense, but even dB Soft themselves released games for the standard X1 BASIC. An interesting decision, I suppose.