For me this so called 'Higher order functions' is exactly how I understand 'closure'. If I'm right, please add 'this is what other people called closure' at the end of this section. It surely will clarify the misunderstanding.
On quite a few of the pages, various symbols ( ` < > & ) are showing up as HTML entities in the explanatory and exercise text.
An example from 4.3 on the website:
x > a:is x bigger than a?
x < a:is x less than a?
Which looks as expected on github:
x > a: is x bigger than a?
x < a: is x less than a?
Each of the parts listed above will need a trial duration. For example the fixation cross needs to be shown for 2 seconds, the instructions for 4 seconds, and so on. I'm pretty sure I can loop through the trials, I just need help with how to set up a variable to show the pictures for a specific amount of time.