The function I do suggest is to add the notes for explaining the meaning of icon again (in a simple way), I do suffer from forgetting some (like smiley and heart mean different in the grid or on the side...), still enjoy the game anyway.
Great game, can complete without the premium add-ons. Max the update part and use "SPACE" in battle cleverly would be help for the final HARD level. Another tip I found was that do not upgrade the relics unless you max all the "upgrade" part already, you will get some relics upgrade when passing levels. The advise for the game I think is the chance to get some relics for repeating some challenge/hard levels ( I am not sure but I did not get one after finished all levels). Thanks and nice game!!