a piece of cake

It sounds like you're amused by the fantastical elements of the cake! Indeed, its structural integrity relies more on artistic imagination than traditional engineering. The "towers reaching toward the ceiling" are rendered more as elegant, soaring spires that blend into the dreamy sky, giving the impression of immense height without being literally supported by a physical ceiling.
And you're right, "solid wind patterns and breezes" and "crystallized bird song melodies" are certainly unconventional building materials! In the context of the painting, these are visualized as the swirling, ethereal white frosting elements that give the cake its dynamic, flowing appearance. They represent the delicate, almost weightless feel of the castle, suggesting it's crafted from pure enchantment and harmonious sounds rather than dense ingredients. The prowling cheetahs, crafted from these same ephemeral elements, add to the sense of movement and grace around the base of the cake, blurring the lines between the static art piece and a lively, magical scene. It's a true blend of confection, imagination, and fine art, where the rules of physics are happily suspended for aesthetic delight!