Bounzy is the game with the least "RPG" elements, as you only play a single character, a wizard, and upgrade his spells. It plays the most like a puzzle. Your job is to shoot a string of spell missiles at a horde of advancing monsters. Monsters that you don't kill advance further, until they damage your wall. If you manage to kill all monsters, you get some gold, with which you can upgrade your spells. The art is to foresee how the missiles you shoot will bounce, like billiard balls, from the walls and obstacles. Preferably you get your missiles behind the monsters, where the bounce back and forth until the monsters are dead. This is probably the simplest game of the three, with not much bells and whistles added. But it is also the fairest game, which pushes you the least towards spending money. Actually I only spent $5 to show my appreciation, I could very well have played withou spending anything at all.

Flick Heroes has multiple characters to choose from, which you level up. Each fight has your characters and the monsters in a room with some obstacles. You fight by flicking your character against the monsters, with an effect even more like a billiard table. This is less obvious to play for free, as training your characters to the next level takes training slots and time, and without money you only get one training slot.

Angry Bird Evolution has the most bells and whistles, plus the biggest name brand. It is a mix of Angry Birds and a RPG. You build a team of up to 5 birds, and slingshot them in combat against the pigs. Unlike the original Angry Birds games this doesn't involve ballistical flight, again the combat takes place on a billiard table kind of physics environment. Unfortunately this is the greediest of the three games. It uses the old trick of getting harder faster than your birds naturally evolve. Then either you grind scout missions, of which you get only one per hour, or spend money to buy premium eggs and other advantages. Not so much Pay2Win, but the even more nefarious Pay2NotLose.

I can only really recommend Bounzy of these three, and even that gets repetitive quickly.