Pascal's Ball Pit

You're probably familiar with Pascal's triangle, wherein each number is the sum of the two numbers directly above it, with imaginary zeroes occupying the "empty" spaces: ` 1 1 1 1 2 1 1 3 3 1 1 4 6 4 1`You can see that the rows increase in length by one on each iteration such that the triangle "grows downward" over time. For this problem, we'll instead construct an inverted pyramid by applying the same logic but without the imaginary zeroes. In fact, let's do away with numbers entirely and use these instead: 🔴 🔵 🟡. The rules for adding two colors are quite simple: <<1.>> If they're equal, it's effectively a no-op (🔵 + 🔵 = 🔵). <<2.>> Otherwise, the sum is whichever color isn't one of the summands (🔴 + 🔵 = 🟡, for example). Let's start with 🔴🔵🟡🔵 as our initial row and see how the triangle develops: `R B Y B Y R R B R Y`Observe that every "dot" in the subsequent rows is indeed the "sum" of the two dots above it. Note also that our triangle "shrinks downward"; each iteration decreases the row length by one, requiring it to be offset from the left by that much more in order to obtain the triangular shape. Given an integer [[N]] and an initial row of that many colored dots, display the full triangle.