This deck tries to KO 6 of your opponent's Pokemon with heavy splash damage starting early on in the game with Mew and Rainbow Energies, before they can KO 6 of your fragile, 30hp Mews.
Defenders and Focus Bands should only be used on Mews to maximize the amount of times that you can get Rainbow Wave attacks off to slowly break down all of your opponent's health slowly.
If you can't find a Rainbow Energy in your deck/they're in your prizes, if you have 2 Psychic Energies attached to your Mew, Porygon2 can use it's Pokemon Power, Energy Converter from the bench, to turn 1 of those 2 energies into any type you want, to effectively mimic a Rainbow Energy.
Challenge! is effective in this deck twofold if your opponent accepts:
1 - It can be used to bring out all your Mews from the deck to ensure you can Rainbow Wave turn after turn.
2 - Depending on how many Pokemon your opponent drops onto their bench, it adds a ton more targets to do even more damage with Rainbow Wave.
The Starmies are in there for their Core Stream attack to continue pouring on the splash damage if all your Mews have died and you're all out of Revives.