There a 2 types of canvas are:
1- The Game: It's typical C2 canvas. It doesn't require to update the game, also it can be played on offline.
2- The Updated Random Content: like news, ads, extras, bonus, etc. that can be changed content while is connecting the internet, otherwise if there no internet connected, it will be ignored.
When you play as platformer, when you enter next layout or a store building, then it starts to download an external HTML5 canvas, it may be an pop up window or inside of The Game canvas.
Is that possible?