Interceptor Demo update 2021-07-07

Update 2021-07-07:

• Implemented the final enemy type; the torpedo. They take two hits to destroy and deal massive damage to your fleet if they get past you.
• Refactored code that made the project incompatible with newer versions of GBDK-2020, specifically changes to WRAM management.
• Partially completed refactoring enemy spawn and VRAM management. This will:
  • Allow more enemies to be active at once. Currently supports up to six with only a slight drop in performance, though not currently used in current spawn list.
  • Reduce CPU overhead and ROM space usage as the majority of enemy code has been consolidated, removing a lot of redundant and specialized code.
• Added placeholder music for stats screen (accessed by pressing Select from title screen.)
• Enemy behaviors are now tied to the enemy type rather than a value the player cannot see. This should make enemies a lot more predictable.
• Minor optimization to sound effect management by consolidating them into a single sound function.
• Minor visual tweaks for improved visibility against a black background:
  • Black on the enemy palette has been replaced with a dark grey for Game Boy Color mode.
  • Enemy interceptor has had the black lines on the trailing edge of its wings replaced with dark grey.
• Fixed mistake in spawn list that resulted in two identical fighters spawning stacked on each other that perfectly mimicked each others movements. This would appear as an enemy fighter that would not die after the usual two hits.
• Fixed player ship being able to go two pixels out of bounds on one side and not being able to touch boundary on other side.