Puzzle Mode

Puzzle Mode is a game mode in Plants vs. Zombies that contains two (three in the iOS and Android versions) separate puzzle types. It is unlocked on Level 4-6 in a present dropped by a zombie. However, the player can't play all of them until they complete Adventure Mode. This is probably because there are zombies that the player hasn't encountered yet. In iOS and Android versions of Plants vs. Zombies, the player must purchase the I, Zombie, Vasebreaker, and Last Stand (iOS and Android only) game packs. Otherwise, they can only play the first one.

Vasebreaker
In this puzzle, the player has to break open all the vases and collect plants to defeat the zombies hidden inside. Different Vasebreaker levels have different plants and zombies, but there are some features common to most of them. Most contain left-facing Repeaters, and after "To the Left", all levels have two green plant-containing vases with leaf symbols on them. These vases always yield plants. Also, Planterns in "Ace of Vase" and "Vasebreaker Endless" show the contents of the vases adjacent to them. In "Ace of Vase" and Vasebreaker Endless, there will always be a Gargantuar in one of the Vases, and after every streak of ten, one more will appear (the maximum amount being nine Gargantuars). A level of Vasebreaker is also in level 4-5.

I, Zombie
I, Zombie, (its name being a reference to the book and movie I, Robot), is a group of levels where the player must deploy zombies to overcome cardboard plants and to get to the end of each row, where there is a brain. The level is over when all of the brains have been eaten (the player wins), or there are not enough Sun to place any zombies onto the lawn when not all the brains are eaten and there are no any zombies on the lawn (the player loses). At the beginning of the first level, Crazy Dave tells the player that the zombies want to practice invading houses, and as he didn't want any plants harmed, he put cardboard plants on the player's lawn. It is believed that Crazy Dave made the plants come to life with his Magic Taco.

Last Stand
In this Puzzle, which is exclusive to the iOS and Android versions, players are given an initial amount of 3000 for Day and Night levels, 4000 for Pool and Fog levels, and 5000 sun for Roof and Endless levels. Crazy Dave has chosen several plants suited for that level for the player. The difference between the Mini-game and Puzzle Last Stand is that between zombie waves, removing plants give a refund of sun equivalent to its cost, although damaged plants are removed without refund (applies to Pumpkin, Garlic, Wall-nut, Tall-nut and Spikerock) and upgrade plants will only get the cost of the upgrade itself (for example: if you remove a Gold Magnet, you will only get 50 sun from the Gold Magnet, not the other 100 sun from the Magnet-shroom).

Strategies
See Puzzle Mode/Strategy Guide.

Trivia

 * The music playing during I, Zombie and Vasebreaker is "Cerebrawl" (by Laura Shigihara). This is both because the player is both fighting for the zombies (plants in I, Zombie) and the plants (Vasebreaker) but must also use strategy to win.
 * Cerebrawl is a bad pun off the term Cerebrel.
 * I, Zombie and Vasebreaker both take place at night as there are mushrooms in both I, Zombie and Vasebreaker.
 * If you complete a Vasebreaker level that you have already done, the money bag gives two Gold Coins, but in the I, Zombie levels it brings five Gold Coins, making I, Zombie a more efficient replay-type way to get Gold Coins.
 * I, Zombie and Vasebreaker appear as separate game modes in the Windows Phone 7 version.
 * The cardboard plant sprites in the DS version of I, Zombie use the same sprites as the normal plants.
 * The cardboard plants on the iPhone version look a little different and more realistic, but they look like as if they are slightly leaning.
 * There are ten achievements about Puzzle Mode. Three are about Vasebreaker (Smashing!, China Shop and Gotcha!). Three are about I, Zombie (I, Win, Better Off Dead and Where the Sun don't Shine). Three are about Last Stand (Still Standing, The Stuff of Legends and Hammer Time!). The last one is about the whole Puzzle Mode, Think Hard, which is only acquired on the DS version.
 * Conveniently, Puzzle Mode can't be activated until beating level 4-5 on most versions, after obtaining the Magic Taco.
 * However, on iOS and Android versions, it is activated after level 2-2, making it possible for zombies to be encountered earlier on in the game.
 * But they won't be added to the almanac until the level is played in adventure mode.