Update 2020-06-19

Not much observable progress but here goes.

• Refactored code
• Enabled air jump
• Added a sprite flash effect on hit
• Added an invulnerability window for the player after taking damage
• Changed scene layout
  • Added an opening to the left to reload the scene
  • Extended the scene upwards for verticality
  • Added a small scene to test transitions between scenes
• Added an intertitle (is that the right word)?