Roboquest

Found in the Quarry area after unlocking the pickaxe door, and progressing through to a door locked with a keypad. Inside the locked door is a shovel, semi-hidden on a lower floor. To do so:

1. Defeat your first boss and unlock the Ruins area
2. In the Ruins area, deactivate the 4 laser blocking a pipe entrance.
(Note: 4 switches scattered in the immediate area deactivate them. One is on a truck in front of the pipe, one is on the area above, one is in the tunnel, and one is above attached to the underside of a billboard.)
3. After the laser pipe, pickup the blue keycard. You'll use this later on.
4. In the Fields area, after progressing to the green safe-point (halfway through,) there is a locked door. Your blue keycard will open this. Inside is a healing bot, a chest, and the pickaxe keycard.
5. In your next run, you'll now be able to open the pickaxe door. This unlocks the quarry.
*IMPORTANT*
In front of the pickaxe door is a number combination. Memorize or write it down. It was 333 for me.
6. Progress through quarry until you reach a gold area on the map. There is a locked door. Open it with the combination from earlier.
7. Inside the room, press the TNT switch for some easy kills, and collect your shovel in the room.