Dig-N-Rig is a very interesting addictive free game. The most interesting thing about it is the entirely text/ASCII based interface which is surprisingly beautiful, rich, responsive and mouse-friendly.
The goal of the game is to mine down more and more into towards the center of the Earth and collect minerals in the process which can be used to upgrade your stuff and rig. Your mining is assisted by vertical and horizontal conveyor belts so in the end you will have a nice system of these.
I finished the game in 4 hours but I am sure it can take longer if you are not taking the shortcuts that I took: instead of building conveyors and vacuuming minerals towards them I drilled down very deep, built a horizontal conveyor there then ground the whole section above the conveyor belt. This way the minerals that fell down were automatically transported up, no need for vacuums. In the end all I had was a very tall vertical belt and one horizontal at the bottom.
Download the Dig-N-Rig game for free