Pinger was written for Ludum Dare 29. Ludum Dare is a 48 hour game development competition where entrants are not permitted to work in teams, or use prior assets. There is also a Jam, which has less stringent rules. Ludum Dare 29's theme was Beneath The Surface
About Pinger
In Pinger, the player must mine all of the underground gold without running into water. The player uses sonar to locate items underground.

In Figure 1, there is gold three blocks away from the player. The player has deployed one pulse. The gold circle shows the distance to the gold.

In order to triangulate the gold, the player needs to deploy more pulses. In figure two, two pulses have been deployed. By looking at the points where the arcs intersect, we can tell that the gold piece is either two blocks to the left and one block below, or two blocks to the right of the player. By deploying a third pulse, the player has located the gold in Figure 3. (Red circle added for clarity).

Figure 1
Figure 2
Figure 3
Gameplay Video
How to play

The player can only move vertically or horizontally. To move, click on any square that is in the same row or column as the player.

Press the spacebar, or click the "Pulse" button, to deploy a pulse. Pulses last for about two seconds. When the pulse travels over gold, a gold ring is placed. When the pulse travels over water, a blue ring is placed. These rings last for about fifteen seconds each. There is no limit to the number of pulses you create. If your screen becomes too busy, you can press c or click "Clear".

The object of the game is to uncover all of the gold while digging up as little dirt as possible. There is no limit to the number of sonar pulses you can use, and there is no cost to retracing your steps.

There are no known bugs in Pinger. There are known bugs in Internet Explorer. I thought we were past this, but here we are in 2014 and I still have to provide polyfills. If you're audacious enough to use IE, don't expect any sound.