Here is the full list of all 9 Arcade Classics Playtest achievements.
Completely drain a full bar of power boost in one go.
Take aim without ever firing.
Have 3 or more shields in your inventory.
Activated the triple cannon.
Break 4 blue bricks in a row without dying.
Lost a ball to an exploding brick.
Powered up the red ball.
Stock up a total of 5 shields and missiles combined.
Safely guard the city buildings through to wave 8.