It doesn't
feel like I'm learning, it feels like a typical high school quiz. You present information (without ever ensuring I've
learned it) and then check if I've "learned" it with a simple input that requires no thought.
Compare it to the codecademy courses, they introduce you to concepts, explain them and then ask you to perform a task based on what you've learned, whereas with yours it shows a bunch of information and doesn't ever explain what it is or why/how it works.
For example the first 2 exercises (labelled #1 and #2) ask me to modify CSS properties, but then on the 3rd you start teaching how to write HTML and CSS. Surely the 3rd should come first, because without understanding what css is how does changing values help teach me anything?
The interface isn't too bad though, so it's a reasonable start, good luck :)