Teckstack: Question-Based JavaScript Practice

Hi, I recently launched a site called Teckstack which offers quizzes on JavaScript knowledge. The content is pretty basic at the moment, but am looking for feedback, and direction on where I should take things. Go deeper into more interesting JS territory, or expand to React, or Web APIs or Node, or HTML/CSS, or build more features for usability?

Let me know what you think, or if you run into any issues. Apologies up-front if the site mistakenly marks your answers incorrect! I will do my best to resolve any of those issues in a timely manner.