Surely, you’ve heard of xkcd. This webcomic (which sometimes requires explanations for non science-fluent readers), has been running it for almost 20 years now, and there is enough content on its website to give you reading material for days.
One entry, in particular, will certainly have you spend more time than you planned on it.
Simply titled “Machine”, this entry is not an actual comic, but an interactive weird-machine-builder. The cell you see is just a part of a huge Rube Goldberg machine, in which colourful balls enter the frame from one point and must leave it from another point.
The goal is for you to make sure the path of the ball is constant, using your best knowledge–or lack of knowledge, if you are like me–of physics, along with a lot of weird tools from a toolbox at the top right corner of the frame, and so much trial and error.

Once you’re done, you can press the button at the top left to submit your work and become part of the huge collaborative machine. And if you’d rather skip the DIY, you just have to click on “View machine” at the bottom right, which will allow you to spend hours the product of all those genius minds.

xkcd: Machine