Shock Crystal Harvest

Background
You must collect 50 shock crystals from the "Lost Cave."

Walkthrough
You have to go into the cave, find the crystal stashes, shoot them, and then collect the ones that fall on the ground.

This is really difficult if you're <= level 13, unless there is a trick.

One trick is to enter the cave, rush to the first crystal stash, shoot it, collect it, then run for the cave exit. The next time you enter the cave, the crystal stash will be reset and you can repeat. You get 5 crystals each time.