The game will eventually show you how to make combos, but when the levels get tougher, you’ll want to focus on creating combos of five or more cube. When you form a square with four cubes of the same color, that clears any other adjacent cubes of the same color as well, thus allowing you to hit combos of well more than ten cubes if the placing is right.
Item cubes are your power-ups in Green Planet: Clean Up Quest, and each of them have their own special capabilities. Fire cubes shoot fire from all directions, and are designed mainly to take out monsters. The green item cube clears out any purple (or contaminated) title that’s above or to the left or right of it and turns it green. These are the most common that you’ll find in the game, and arguably the most useful on the majority of levels. There are, in fact, levels where you have to clear up land using nothing but item cubes.
Once you see the item cube with a timer on it, work on creating squares or combos (preferably squares for simplicity) so you can clear it and buy yourself some additional time. When you get to Level 15 or so, you’ll realize how important time is when the levels get challenging.
That’s simply by clearing more and more levels with three stars – anything less won’t earn you any acorns. Acorns are the game’s premium currency and you’ll use this to buy power-ups and other items, and while you’ll get one acorn per three-star level, you can only earn it once per level – replays don’t count here!
The pumpkin monsters don’t “attack” – they just stay put and make it harder for you to make combos. The trees, however, move whenever you see arrows next to them, and work to block your path and thwart your attempts to purify the land. With that in mind, you should focus on getting rid of the trees as soon as you could, as it should be smooth (or smoother) sailing once they’re gone.