The theme has icons based on the elements found in the game. SFX effects were taken directly from the game.
If you want to learn how to create custom themes with the same quality of the official themes of Nintendo access this link - https://gbatemp.net/threads/tutorials-to-create-custom-themes-with-the-same-quality-of-official-nintendo-themes.460823/
My gallery https://themeplaza.eu/themes?query=User%3ARyumaru&sort=newest
Editable textures can be downloaded here.