Beneath The Surface
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).
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.