Unlock Arcade Levels 
Finish levels in story mode to unlock them for Arcade play. 

Unlock Gallery Art 
Each time you finish a level, concept art for the level in question will be unlocked for viewing by accessing the Extras menu. 

Defeating Eldridge:
Wait until he is walking toward a barrel and gets close to it. Then, shoot the barrel 
and it will explode, flipping him over. Start shooting him after he flips over. Later 
in the fight, he will start charging you. When this happens, run along the walls until 
he runs into one, then start shooting him.

Defeating Nathaniel Payne:
Use your shovel like a baseball bat. Hold X and release when he throws a chunk of 
rock at you. Do not get the rock confused with the energy ball that is thrown. 

Defeating Trisha:
When she opens her mouth, throw a piece of dynamite into it.

Crystal order at the museum: 
The order to insert the crystals is red, yellow, blue, green.