Alpha 5 - our first boss battle, two new rooms, some new models and dynamic music

A new update with two new rooms, our first boss battle (Fusioneer, the Weld Warden) and a background track that dynamically adapts to the player's style level.

Complete changelog:

feat(enemy): fusioneer, the weld warden - a boss with three weapons and shield generators
feat(enemy): badass fusioneer intro animation with shader stuff
feat(enemy): fusioneer health on screen 
feat(level): the weld chamber, a giant arena for the weld warden battle
feat(level): the dance floor area, a room filled with conveyor belts and jumppads, accessed by two elevators 
feat(general): checkpoint system - some areas unlock checkpoints  
change(ui): the background in the main menu now reflects the actual level 
change(ninja): reduced the translocate's cd to 1
change(vanguard): the charge ability's attack procs damage more frequently now 
asset(general): some new red materials 
asset(enemy): broken fusioneer
asset(general): new dark green, light green and rotten green material colors  
asset(level): 4 new crate models 
asset(level): a new meeting table model 
asset(level): 3 new potted plant models 
asset(level): a new conveyor claw model 
asset(enemy): fusioneer shield shaders  
asset(vanguard): frontal shield shader  
asset(general): awesome background music  
asset(enemy): fusioneer model
fix(ui): option slot sfx not playing 
fix(level): some backtracking fixes
fix(weapon): laser weapon hitboxes are less buggy now