Missing systems and mechanics to complete the demos

[NathanLovato]

This issue is to help me keep track of what main parts of the project are still missing

• [x] Health component
• [x] Combat: taking damage, damaging enemies, death
• [x] Respawn and checkpoints
• [ ] AI system and Enemies
• [ ] Level design
• [x] Visuals
• [ ] Sound
• [x] Transition between frames