- Added a shop with 3 items to select from

Added 3 items:

- Brain: Double the value of gold and XP

- Weights: Gain 3 attack

- Eyedrops: Increase fire rate and bullet speed

- Enemies now follow you regardless of where you are on the map

- Controls are now shown in-game

- Updated main character walking sound

- Changed movement of dropped XP and gold pellets.

- Other minor changes