In Chicken Invaders 4, the yellow key glow is assigned to a randomly chosen enemy after a certain delay.

The enemies eligible for this include all types of Chickens, Eggs, Barriers and Space Burger droids. Most boss waves won't have key spawns, unless if the boss can spawn Chickens as one of its attacks (Planetary Egg City, Chicken Multiplicity, Egg Cannon). This game also has an annoying stretch of 19 waves where it is impossible to gain any keys, which is the retro chapter and most of the supernova chapter.

Unlike in Chicken Invaders Universe, there is no requirement to kill some enemies first to unlock key spawning.

The delay between key spawns is randomly decided between two values. These values depend only on the current difficulty chosen.

• Rookie - Minimum delay of 30 seconds, maximum delay of 90 seconds.
  
• Veteran - Minimum delay of 30 seconds, maximum delay of 60 seconds.
  
• Superstar Hero - Minimum delay of 30 seconds, maximum delay of 45 seconds.

Here's a table that sums it up.

Superstar Hero is the best difficulty for farming keys, but new accounts don't start with it. It has to be unlocked first with the next best option, which is Veteran.

Play on Veteran until you get the 40 keys needed to buy Superstar Hero.

The time it takes for the game to spawn 40 keys:

Once you get enough keys to buy Superstar Hero, immediately buy it and switch over to it. You may already have the best key farming option, but sadly for you, you still have 3000 keys left to get at this point. Have fun.

The time it takes for the game to spawn 3000 keys:

Here's the total time that has to be spent on farming keys assuming you use the strategy mentioned above.


For an average player this is going to take roughly 32 hours.
Good thing the save files you may have here don't carry over to seasonal editions or the InterAction studios website version, so have fun spending 32 hours for each version of this game you get to play.

Funnily enough this is only marginally longer than unlocking everything in Chicken Invaders 5.