There are plenty of levels with four stars in them, but managing to get all 4 in one round can prove a challenge. To do this the easy way go to the lab "Oxidants Happen" in the level "Puzzlement". First what you will want to do is go far the the right until you see 3 orange blocks. Theres a star in the middle one so just stack the other two boxes on top to get them out of the way. Working left we see a long red box with 5 coins around the outside. Open up your toolbox and place a bouncy pad under the "hidden" star. A little further left and you will find a shark tank by some more floating coins. Use your toolbox to place the quarter pipe to collect the coins and place a star bridge over the sharks tank so you can collect all the coins without going for a swim (ner ner ner ner). Then take the long red box and drag it over to the first box placing the smaller red box on top so you can collect the hidden star easily. When you go to attempt it you will need to get a 100% combo. If you do the level right you will end up with 2 secret stars, 1 coin Dash Star and a Combo/Coin star.