What are the Yoshi Egg medals for?

yoshis-new-island

Solution 1:

The medals are for a bonus game that you can find at the bottom right corner of the touchpad's screen. If you collect enough medals, you can press the bonus level and play one of Yoshi's vehicles.

Solution 2:

if you collect all 30, you unlock a challenge level. There is a new level for each world.

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