Accessibility
This site is built to be usable with a keyboard alone, with a screen reader, at large text sizes, and without animation. That is checked automatically on every change rather than reviewed once and assumed.
What is checked, and how
Every page is scanned in a real browser at phone and desktop widths for the problems a machine can find, unlabelled controls, color that carries meaning on its own, text that does not meet the contrast standard.
Every page is also walked with the Tab key, because the commonest way a page becomes unusable is not a missing label but a control that focus can never reach, or content trapped inside a box that no gesture scrolls.
Colors are held to the WCAG AA contrast standard against the background they actually sit on, and the ratios are recorded next to the values rather than measured once and forgotten.
Motion
If your device is set to reduce motion, the site honors it: transitions stop and nothing moves on its own. Nothing here depends on an animation to be understood.
Where it is weakest
Automated checks find the failures that can be described in a rule. They do not tell you whether a lesson reads well through a screen reader, or whether an explanation makes sense when it is heard rather than seen. Those need a person, and this statement does not claim they have been.
The study material is in English and Español, and no other language is offered, which is still a barrier for part of this audience, and it is named here rather than left out.
If something is in your way
Tell us what page it was and what happened. A specific report. This control cannot be reached, this text is too faint, is fixable in a way that a general one is not.
Reports go to the same place as everything else, which is the contact page.