Portal Combat

Portal Combat is a Night Mini-game without Graves. Instead, there are two pairs of connected Portals, which Zombies and projectiles will pass through.

Zombies

 * Zombie
 * Buckethead Zombie
 * Football ZombiePortal1.jpg
 * Balloon Zombie

Strategy
This is a conveyor-belt level, where the plants that can be received are the Peashooter, Repeater, Torchwood, Cherry Bomb, Cactus, and Wall-nut.

Be careful of the portals, but don't base your entire defense around them, as they will frequently shift positions. Try to get a Cactus in every lane as fast as you can, although it is a good idea to save up at least one in the Conveyor Belt in case a Balloon Zombie comes where there isn't anything to stop it. Save up your Cherry Bombs whenever they appear, and only use them when you have to (e.g. on Football Zombies, or if a Portal appears in the back, behind most of your plants). Use your Torchwood wisely, as it does not work on Cacti, and place Wall-nuts in front of particularly vunerable Portals.

Trivia

 * Occasionally, portals may appear in positions where, with the same set of portals in a single row, zombies may not be able to walk on a few squares and any projectiles that were fired before the portals switched may be trapped in an endless circuit until the portals move away.
 * The name "Portal Combat" is a pun based on the video game series Mortal Kombat and Portal. The white circular portal is a reference to the latter game series.
 * The achievement No Fungus Among Us cannot be unlocked in this level.
 * When a lawn mower heads towards a Portal, it will teleport to the other set.
 * This is one of the only levels where you should not buy a rake, because if a rake is in the 2nd or 4th lanes a zombie will come there, and teleport to the other side of the portal deep into your defenses.
 * Portals will teleport projectiles, even high spikes which look like they will pass over the portals.