Polyrhythms! Multiple rhythms at once! Let's dive in!
1) An interesting feature of polyrhythms is how each part drifts in and out of sync with each other. For instance, look at the notation below. Notice how the second and third attacks in the top voice kind of flank the third attack in the middle one, each kind of reaching toward the next beat away but not quite making it. And as you get more and more complex numbers, you get even more intricate patterns. Take 7 against 8, for instance. How do the beats in each of those line up? Which ones are closest? Which ones are furthest away? Try to visualize and analyze the entire pattern if you can!
2) Which of the notation methods made the most sense to you? Could you see yourself using irrational meter? Also, as a bonus question, did you notice that weird clef we were using? Do you know what that clef is?
3) Let's try something new: A playing exercise. Try to tap out a polyrhythm. Start with the hemiola, that's simplest. If you can get that down, try 3:4, 4:5, whatever you want to do. The most important thing is to keep each part consistent. Don't let them get pulled into each other's rhythms or you lose the whole effect! If you can't do both parts at once, try listening to a song in 4/4 while tapping along three evenly spaced beats per bar. It's tricky!