Blue Illusion (Hard) is the first stage in Growing Blue.
Shibaliens are sent as minions and after a few seconds, 2 Hyppohs are sent out. Once the base takes some damage, 2 Imperator Saels and a Maawth come out and attack.
Lineup: Macho Cat, Samba Cat, Wall Cat, Dragon Cat, True Valkyrie Cat and Bahamut Cat.
Start the game by upgrading your worker to level 3-4 then spam your three meat shields (Macho, Samba, Wall) and Dragon Cats. After the three Shibaliens have been killed you will notice a few Hyppohs approaching save up for a True Valkyrie Cat while still spamming the three meat shields. Once they are both defeated get a Bahamut Cat and continue spamming the meat shields and Dragon Cats. Wait until the Bahamut kills the Maawth and then win.
Strategy 2 (Farming)
Lineup: Mohawk Cat, Crazed Macho Cat, Eraser Cat, Awakened Bahamut.
Start by getting worker cat to level 3-4 then spam your three meat shields and save up for Bahamut and he should demolish the whole rest of the level. Easy win.