Now that we have our battery collectables in place, we'll need to show the player a visual representation of what they have collected. The textures imported with the batteries package have been designed to clearly show that the player will need to collect four batteries to fully charge the door. By swapping an empty battery image onscreen for one with 1 unit of charge, then for an image with 2 units of charge, and so on, we can create the illusion of a dynamic interface element.
Part of the assets imported with the batteries package was the textures folder. This folder contains five image files — one of an empty battery cell and the others of the four stages of battery charge. Created in Adobe Photoshop, these images have a transparent background, and are saved in a PNG (Portable Network Graphics)format. The PNG format was selected because it is compressed but still supports high quality alpha channels. Alpha channels are what...
