Digger was a video game designed by Windmill System to run on IBM PC compatibles using Intel 8088 8Mhz machine on CGA 4-color displays back in 1983. It used to run tolerably fast on IBM PC-AT with 80286 16Mhz chips. However, by the time 80386 PC comes about Digger no longer runs at a playable speed.

Now, it has been lovingly reversed-engineered by Andrew Jenner to run on modern Pentium machines, and in Windows 9x. You can get the software for free at http://www.digger.org/. This is a recommended retro game.