Most achivements are gained from starting and completing levels, however there are some exceptions:

★!
Click on an explosive in the star on level Z.

❤!
Click on an explosive in the heart on level K.

⟲!
Restart a level (duh).

Settings!
Open settings (duh).

Winner!
Beat all levels.

Portal
Use the portal in level P.

Zup Bro!
Click on the Zup logo in the menu.

Orange, Beige, Yellow, Red, Dark Blue, Green, and Turquoise (All Solid Color Achievements)
Click on the zero in the menu.

NOTE:
To get all 3 trading card drops play the game for 2 hours.