Survival: Endless is a Survival Mode level that is set in the Pool which has an unlimited number of flags. It is featured in all of the versions of Plants vs. Zombies, along with Plants vs. Zombies: Journey to the West and Plants vs. Zombies: Great Wall Edition. It is unlocked after completing all the other Survival Mode levels. This level is mainly a challenge of surviving as many flags as the player can, and will become very difficult as the player completes more flags. Just like all Survival: Hard levels and Last Stand Endless, the player can choose new plants when two flags are completed. Each time the player upgrades a plant, the upgrade's sun cost increases by 50 sun. If an upgraded plant is removed in any way, its cost will decrease by 50 sun.