Looks nice, easy to navigate. I would have the munu collapsed until you reach a section as otherwise it may put the user off with how much content you have.
There are some little issues, early on one of the bullets is black not blue, on the sorting exercise the right hand bottom text is either the wrong colour or emboldened.
the first drag and drop the text is pixellated because it is an image, I know why you have done this but, you can edit the normal state and add your text and picture instead of saving it all out as an image.
I really like the click on boxes and, your UI skills shine here using a drop shadow and gradient so the user knows to click
You do have some pixellated images such as the engage timeline screenshot. This is probably worse because the player is set to scale.
Just being picky but on the ASK ineraction the initial A drop shadow is messing up the image a bit (just being picky).
The real positive is I wanted to complete the course, as a lot of time I never get to the end. Well done :-)