Shoot the wooden crates branded with question marks hanging from the tracks above. They may drop coins or blobs as well as monsters. Do not use rapid fire or you may hit a blob.
Missions
Missions will become available after the level 1 is completed. They are side objectives that are completed as you progress naturally. A red number next to a mission icon indicates that you have a mission ready to turn in in order unlock more of them. Each mission completed rewards you with gems, the game's premium currency.
Monsters
The deeper you progress into the cave, the more dangerous the monsters. Mine tracks may give signs such as exclamation marks or skulls that indicate that a big monster is near. White circles that appear above you usually indicate flying monsters. They frequently attack in big groups when in larger areas. When something is out of your light range, it will appear as a white circle as you approach. A white circle that remains stationary is probably a blob. A white circle that begins to move before your light radius touches it may be a monster.
Shotgun
The shotgun is the next upgrade to the pistol in the weapons tree. It works similarly to the pistol, except it fires two angled shots in addition to the standard straight shot. Watch your aim to avoid hitting blobs. It is also slightly more powerful than the pistol. Consider using it over the submachine gun.