I understand it is probably not your top priority, but could you maybe pick one-two fonts and use them for everything?
Plus you can remove backgrounds, unnecessary colours, unnecessary boxes which will make the design much cleaner.
Another thing would be consistent position of buttons and indicators (the gold/rubies is in bottom-left on main screen, but is top-left in the shop)
One suggestion, if there are no bubbles of a given colour left on the field, but there are left in the "gun", please consider it as if the field were cleared from the colour. It's very annoying to remove all the bubbles of one colour only to find it reappear in your gun.
“I see you moved your mouse away from the screen, I'm going to move your character all the way to the top-left corner through all the bullets. That's what you wanted to do, right?”
I'm not sure whether it was mentioned before but the graphics (or at least majority of it) comes from the Majesty: Fantasy Kingdom Sim game (https://play.google.com/store/apps/details?id=com.herocraft.game.majesty&hl=en)
There is absolutely nothing in this game, that should lag this badly. You should not improve graphics, add features, eat and sleep until you optimize the code
For those who talk about "Doodle god clone". The doodle is also a clone of an Alchemy game http://www.steinruecken.de/alchemy/, so its like call each tetris game a "Tetris clone".
 "Chess Evolved Online"){kind=icon}
 "Reach the core"){kind=icon}
 "Wrath Of Zombies"){kind=icon}
 "Bubble Shooter Classic"){kind=icon}
 "Bear in Super Action Adventure"){kind=icon}
 "Decision 3"){kind=icon}
 "Royal Offense"){kind=icon}
 "Battle without End"){kind=icon}
 "Into Space 2"){kind=icon}
 "Pinata Hunter"){kind=icon}
 "Lead for Dead: Call of the Dead"){kind=icon}
 "Another Cave Runner"){kind=icon}
 "Reactance"){kind=icon}
 "Evolution"){kind=icon}
 "ccc-Chain!!"){kind=icon}
 "Backyard Sports: Sandlot Sluggers"){kind=icon}