What are cannons for on the world map

Collecting all three star coins on every level in a particular world opens up a corresponding secret level in the correspondingly secret World 9. For example, if you get them all in world 3, you unlock world 9-3

You need to collect every star coin from all nine worlds to achieve the second and third of the five save file stars, which indicate how much of the game you have completed.

You can also use them to buy videos like "super skills" Or "Star coin".

There are 14 secret goals to be found in the game.

here's the list and where they are.