Rewrite start
Add make function in utilities
Reimplement Box and Vector2
Add alive property with start and stop function
More better implementation of state-based game and add update and draw function
Add tick function and comments on update and draw function
Edit comments
Refactor, and add asset manager
Add input manager

I have no idea how to handle input, so for now, this is it.
Edit Box and Vector2
Add Entity
Add squaredLength in Vector2
Remove make global function (still in utilities)
More useful way to make objects
Add more comments
Add default properties
Rename deepExtend to deepCopy (because it's a better name), and reverse the order of parameter in deepCopy
Add the basics in core.js
Fix errors
Fix some errors