Each time you defeat a Koopa Kid when it's your turn, another one will walk in with the same or different color. Here are the tricks to each of the colors:

Blue: This one is slow and generally the easiest to deal with. They are immune to Luigi's thunder.

Red: This one has a faster speed than Blue and can shoot fire. The sneak and barrage attack both have Red spew fire at Luigi. They are immune to the hammer attack during your turn.

Green: This one is very fast and known to be the tough one. They are immune to the jump attack during your turn.

Attacks:

Barrel Sneak - The Koopa Kid turns around and a barrel lands on Luigi, who then has to sneak to the enemy and bonk them with a hammer. If you're caught, you'll get sent back flying to your original position. A chandelier can fall from the ceiling and will make the enemy turn to face you immediately when it hits the floor.

Koopa Barrage - Every type of Koopa Kid will run towards Luigi in large numbers. You have enough room to run from 3 spaces and can hit the enemies with your hammer as they run past to deal extra damage. This is the best attack for damage, so hope to get it often.

Fire Machine - A transition will happen, and Luigi will be transported to the middle of the screen. A regular Koopa Kid will be inside a big machine and shoot 3 spews of fire. The front and back ones are just for show, but the middle can hurt you. The other fire spews can also tell you if you need to duck if they jump up while moving. This is your chance to charge up Luigi's super jump and grab the star coin that spawns at the top of the screen.

Bowser Suit - Another transition attack that will move Luigi to the middle of the screen. A Koopa Kid will be in a big Bowser suit and curl up into his shell, signaling for the Shy Guys holding the trampoline to bounce him towards Luigi. You have to watch out and jump over the shell from a 3-dimensional perspective. Each time the shell hits the trampoline, both its horizontal and vertical speed will change each time.

That's the first enemy done for update 4.0. I hope you enjoyed and are looking forward to the next update!