Celadon Gym

Description
The level begins with you and Joey reaching Celadon City. As the two of you talk about finding the gym leader and releasing them from Mewthree's control, Celebi appears and speaks with the protagonist. Celebi informs you that it has come from the future to save its past self, who is being mind-controlled by Mewthree.

The three of you head to the gym and find Erika, who accepts your challenge.

In the level, Joey's Charmeleon and Pidgeotto will attack enemies. Celebi will heal your towers' health every so often. These three Pokemon will not be targeted by enemy attacks.

Layout
Waves: 16

Spots: 19 [12 Normal (2 Taken), 7 Grass Only (1 Taken)]

Defending: Rare Candy (10)

Strategy
The enemy waves appear in a pattern: top left, bottom left, bottom right, top right. This repeats until the end of the level. If you can memorize the pattern, you can easily set up for the next wave before it appears. If you can't memorize it, keep scrolling around the screen at every moment (use the Pokeball to stop enemy movement if necessary) so you can quickly move your towers to the enemy Pokemon.

Bring fire, bug, and ice types that have strong moves like Fire Blast, Bug Buzz or Blizzard. Keep Pokemon that are weak to grass moves away since the enemy Pokemon will attack you.

A Butterfree with Psychic or Bug Buzz can be useful since most of the Pokemon are Grass/Poison plus it's Flying/Bug typing makes it fairly resistant to grass attacks. Same for a Charizard with Fire Blast, it's typing (Fire/Flying) is resistant to grass moves.

A Parasect with Aerial Ace would be a good addition to the team since it can be placed on the Grass only spots. Venusaur with Roar would also be useful if you need the extra hard hits from your main attackers.

When you see Celebi, be sure to remove all your towers out of the way. It is extremely powerful and can easily take out your best Pokemon with a Solar Beam or two. Celebi appears as soon as the wave number changes to an even number as the only Pokemon.

If you want to defeat Celebi, use the move Bug Buzz on it, as Bug is super effective against Celebi's Grass/Psychic typing. Or, bring an army of Charizards with Fire Blast.

I used 2 level 44 charizards using Fire Blast,1 level 44 Venusaur using roar,1 Butterfree using Psychic and two other pokemon using flamethrower

I placed the Venusaur at the bottom when the venasuaur wave was going by but the other times I had the charizards battle all the other waves except the bulbasor wave when I used the butterfree using psychic and I used the other fire type pokemon when the venasuor wave was going by, I placed them ahead the other waves.

Using Butterfree with SIlver Wind also is a option, due to it raising its stats to increase damage and to take less damage from attacking pokemon.