Learning complex topics like algorithm complexity etc requires quite some time to understand. You can start putting a base on them by understanding them as ideations.
Microideation app was created as a lockdown project and now has content on various topics explained as ideations ( An ideation is a concrete explanation of a topic within 500 characters created by subject-matter-experts on the field using rich formatting and images). You can use this as a casual method of learning or refreshing of your memory on the topics that you already work on.
You can navigate the ideations using simple swipe gestures and each swipe brings up a new unseen content based on preferences. Freeze and follow a subject ( like complexity ) and see the entire content. There are also links to other ideations that you can refer to.
Download the app ( no registration and it's free )
Visit the portal and contribute your content