Preload code for the buttons changed to load spritesheets
Preload code for the buttons changed to load spritesheets

Originally they were using static buttons but now:
* btn-start.png -> btn-start-sprite.png
* btn-credits.png -> btn-credits-sprite.png
* btn-help.png -> btn-help-sprite.png

Still keeping old buttons just in case.

OdinsHat/drac