 So it's pie day. Gotta make a pie. And there's two parts to making a pie. The crust and the filling. Say a blackberry filling and a butter crust. Sugar goes in the filling, salt goes in the crust, but there's flour in both the filling and the crust, so that's convenient. We only have to add it once. Then grab your ven spoons and mix it up. Yeah, that's looking pretty good. And here's our finished crust. And since we're tau fans here, let's make two pies. That intersect. Okay, in goes a blackberry filling. In, in, in. But what filling for our other pie? Let's use fresh peaches. Chop, chop, chop. Okay, there we go. So we have a blackberry peach ven piagram, but what goes in the middle? You might think a mix of the two for a blackberry peach pie, if you're thinking of each pie section as an entire category. But if you're thinking of each individual thing in each section, it wouldn't make sense to put peaches in the blackberry circle or blackberries in the peach circle. And there's no fruit that's both a blackberry and a peach yet. But maybe you could put plums in the middle and have the categories be stone fruit for peaches and plums, but not blackberries. And then both plums and blackberries, but not peaches, are in the category of fruit that you can eat without feeling weird about biting something so soft and cuddly. Then you could put apricots in with the peaches, nectarines in with the plums, and lots of stuff in with the blackberries, if you wanted. But I don't have all that, and we need something for this middle section. And the obvious answer is fish. Fish makes sense. Because the pointy ovally shape of the middle section, if the circles are overlapping so it's that they intersect each other's centers, this shape is called vesica pisces. Pisces like fish, and vesica means bladder. Fish bladder. That's what this shape is called, so I put fish in it. Well, people put fish on pizza, and that's a kind of pie. Okay, so it's pie day, gotta make a fish pizza pie. Pie has two parts, the base and the toppings, and the dough is the base, and the tomato sauce is somewhere between a base and a topping. I mean, I'm from New York, so I have opinions, but sure, now that I'm on the west coast, I can accommodate people who think even cheese is optional by thinking Venn diagrammatically about my pizza, instead of just having black and white opinions about everything. And in the last section goes things that are just topping and not standard pizza base, like anchovies. Okay, so we're going to have two overlapping pies, one for saltwater fish and one for freshwater fish. Anchovies are saltwater, so are mackerel, and then some freshwater trout, and you know what's a freshwater fish and a saltwater fish? Salmon! All that work to swim out to sea and then jump back at waterfalls to spawn just so they can end up in the honorable Vesica Pisces position of the pie day Pisces pizza pie diagram. Okay, let's get that in the oven, but how are we going to cut it once it's done? Luckily Euclid figured this one out thousands of years ago, just pretend you're doing a ruler and compass construction of the equilateral triangle. Draw a line through the two circle centers, then lines from the centers to the circle intersections. And if you actually wanted to use a number pie today, here's some homework, and it actually smells really good. Let's check it out. Oh, perfect. There we go. A pie day Pisces pizza pie diagram. Okay, happy pie day. Bye. Oh wait, let's do Euclid to it. Okay, yep, we sure did some geometry to a pie with fish on it. Okay, bye.