Marbleslides: Rationals starts simply but ramps up in difficulty. The true brilliance of the activity emerges in the later levels, known as "Challenge Creators" or complex puzzles where stars are placed in devious locations.

Suddenly, the domain is not just a notation written in set-builder form ($x \neq h$); it is a physical constraint of the game mechanics. A student cannot simply draw a line through the asymptote to get a star on the other side. They must strategize.

In the "Rationals" edition, the marbles don't just fall straight down. They follow the curve of the function. If you write $y = \frac1x-2$, the marble will race down the right side of the vertical asymptote at $x=2$, then jump (infinitely) to the left side.

Students learn how adding or subtracting constants affects the graph. Changing