Where the Sun Don't Shine

Difficulty: Medium-Hard

How to get
This achievement requires beating I, Zombie (Level) with 1000 Sun remaining.

Strategy
There are some Squashes, Peashooters, and Snow Peas with the Sunflowers. The Zombies that are available to you are the Zombie, the Buckethead Zombie, and the Football Zombie. You should always place the Zombies on the column right next to the red line. If there are no Peashooting Plants in a row, put a Zombie there. If there is a Squash, put two but space them out or else the Squash might kill both Zombies. If a row has only Squashes, use four Normal Zombies. If the defenses are below the minimum defense (see below), use a Normal Zombie. Anything above, use a Buckethead Zombie. If you have a row full of Snow Peas, maybe a Football Zombie is recommended. Usually you shouldn't have to use a Football Zombie at all. Make sure to use normal Zombies to eat the Brain.

Trivia

 * This is one of 10 Achievements that are in Puzzle Mode, the others being Better Off Dead, China Shop, Think Hard, I, Win, Smashing!, Gotcha!, Hammer Time!, Still Standing and The Stuff of Legends.