Here is the full list of all 14 Summertime Madness achievements.
Make new friends
Look at all the Graffiti
Explore all the Voids
There is something in the water
A hidden show
Light the sky
Play THAT SONG on the piano
Catch 100 Butterflies
Complete the game in Advanced mode
Find all the instruments
Complete the game in Expert mode
Complete the game in Classic mode
Find a special place
Turn on the TV