How do I get rid of the mosquitoes in Level 256?

Open the brown door on the right and let all four mosquitoes fly out.

Do I need to use Doctor Worry's fly swatter?

No. The swatter is the obvious decoy; the open doorway solves the problem.

At least one mosquito is still inside, so keep the door open and wait for the last one to exit.

Brain Test 4 level guide

easy 6 colors

Brain Test 4 Level 256 opens the brown door so all four mosquitoes fly outside, bypassing Doctor Worry's tempting but useless fly swatter.

If the player asks you to sign in, open the video on YouTube instead.

Colors in this level:

White, Brown, Blue, Black, Red, Green

Trying to swat each mosquito even though the fly swatter is only a visual decoy.
Closing or ignoring the door instead of giving the insects a route outside.
Assuming the puzzle is finished after only one or two mosquitoes leave.

Board notes 5 details

Layout: Doctor Worry holds a blue fly swatter near the lower center, four mosquitoes circle above a brown armchair, and a closed brown door stands on the right.
Goal: Open the right-hand door and wait until every mosquito leaves through the doorway.
Opening: Press the closed brown door and pull it open instead of chasing the insects with the swatter.
Danger Zone: The swatter invites individual attacks, but the level clears only after the open door lets all four moving mosquitoes escape.
Mechanics: A single environmental change creates an exit, after which the mosquitoes leave automatically one by one.

How do I get rid of the mosquitoes in Level 256?
Open the brown door on the right and let all four mosquitoes fly out.
Do I need to use Doctor Worry's fly swatter?
No. The swatter is the obvious decoy; the open doorway solves the problem.
Why has the green check not appeared yet?
At least one mosquito is still inside, so keep the door open and wait for the last one to exit.