Driller was the very first Freescape game. A very important game for its time. It first came out in 1987.
It was one of the first ever games that allowed you to explore a full 3D environment, and Freescape was the engine that made it possible.
During play you can rotate the first-person field of view and also look up and down. You can choose whether to step or turn in increments. And you can shoot objects in the environment to interact with them. Shoot a tank to destroy it. Shoot a door to open it. Shoot a switch to activate it. And so on. The puzzles are simple, but for the time the engine was mind-blowing.
The Amstrad‘s extra colours and decent frame rate make this version the best of the 8-bit originals.
The Amiga and Atari ST versions take Driller to another level though.
More: Driller on Wikipedia