The level consists of eight Platforms and a Propeller, and also contains two Clouds. Six of the platforms are in a diagonal line from the bottom-left to the top-right of the screen, with the Propeller in the middle. Five of the Balloon Birds in the stage spawn on these platforms, on all except the lowest one. The lowest Balloon Bird is pink, the next three going upward are green, and the one at the top is yellow. One other platform is located in the top-left of the screen, and one more yellow Balloon Bird spawns on it. There is one last platform that is right over the water, and is slightly longer than the other platforms. One cloud is by the stray platform in the top-left, and the other is slightly above and to the right of the platform over the water.
It is likely that there are only six Balloon Birds due to the limitations of the NES, as only up to eight sprites could be rendered on one scan line, with any more leading to flickering.
After Phase 12, the stage will be repeated for the rest of the game, as Phases 16, 25, 34, 43, 52, 61, 70, 79, 88, 97, A6, B5, C4, D3, E2, F1, G0, G9, H8, I7, J6, K5, L4, M3, N2, O1, P0, and so on.
This phase was almost entirely redesigned in Tingle's Balloon Fight DS, with only two of the six platforms in the diagonal line remaining, with just four green Balloon Birds spread across the remaining platforms.