How do I reach the key in Level 12?

Move left from the crate, jump onto the upper horizontal platform, cross it toward the right, and jump from that height into the yellow key.

Why is the right-hand door chained?

The chain marks the key gate. Collect the yellow key first, then return to the lower floor and enter the door.

Mr Potato level guide

medium 1 colors

Use the crate and upper floating platform to reach the yellow key, then return to the right-hand door after it unlocks.

Layout: A wooden crate marks the lower starting area. A horizontal floating platform crosses the upper middle, the yellow key is high on the right, and a chained door waits on the far-right ledge.
Goal: Collect the yellow key and use the now-unlocked arched door on the right.
Opening: Move left from the crate, line up under the floating platform, and jump onto it before attempting the key.
Danger Zone: The chained door is inaccessible before the key, and a low jump from the floor will not reach the upper route.
Mechanics: The yellow key is the exit gate; the crate and floating platform provide the vertical route needed to collect it.

Use the crate as a positioning landmark, then take the upper platform rather than attacking the door from below.
Cross the platform before jumping for the key so the jump begins from the required height.
If the board feels stuck, look for the color with the cleanest path and use that to regain space.

Move left from the starting position beside the wooden crate and line up below the floating platform.
Jump up onto the horizontal platform and stabilize on its surface.
Move across the platform toward the right, then jump into the yellow key to collect it.
Return to the lower floor near the crate and travel right toward the exit ledge.
Enter the arched door once its chain has cleared to complete the level.

Colors in this level:

Yellow

Walking straight to the chained door before collecting the key leaves the exit locked.
Jumping for the key from the lower floor starts too low; use the floating platform as the launch surface.

How do I reach the key in Level 12?
Move left from the crate, jump onto the upper horizontal platform, cross it toward the right, and jump from that height into the yellow key.
Why is the right-hand door chained?
The chain marks the key gate. Collect the yellow key first, then return to the lower floor and enter the door.