Implement an Achievement/Trophy
feature. 

Add an in-game Achievement screen you can open from a pause
menu in the Overworld. The screen should show Locked and Unlocked
Achievements, with descriptions of the requirements for each one. When the
requirements for one are met, a popup prompt should appear for a few
seconds to notify the player that they have unlocked that achievement. Add at
least 2 unlockable Achievements: 

1. Take 10 steps in the Overworld
2. Open the Achievements Screen