A free app for Android, by Yso Corp.

Pen Dig is a casual idle game for Android phones. In this game, you will use your fingers to dig stones, break rocks, and collect money. You can use the money to upgrade your tools or build your own city. You will need to get started by opening a mine and digging for gold. As you dig and break rocks, you will earn money. The more money you earn, the more tools you will be able to upgrade. When you are ready, you can travel around the city with the vehicle that carries the stones and build buildings and open new areas.