Fortress Trap

The Fortress Trap

2 Unlocked at Town Hall 6, then 3 at Town Hall 8.

Cost: 45000 Gold

Effect: After a troop(s) for a total housing space of 20 or more get past it the trap pops up (like a spring trap maybe?), turns into a wall and acts like it. (Doesn't count flying troops).

Level 1 to 3

At Level 1:
Re-Arm cost: 18000 Gold
Looks and acts 1 level lower than the weakest level wall near it (Ex.: If it's between a level 6 wall and a level 7 wall it will look and act like a level 5 wall), will look and act as a level 1 wall if near another level 1 wall. If it isn't near any wall it will look and act like the weakest wall in the composition.

At Level 2:
Level 2 is unlocked at Town Hall 7
Re-Arm cost: 20000 Gold
Looks and acts like the weakest wall near it. If it isn't near any wall it will look and act like a wall that is 1 level higher than the weakest wall in the composition. If all walls are level 11 it will look and act like a level 11 wall.

At level 3:
Level 3 is unlocked at Town Hall 9
Re-Arm cost: 22500 Gold
Looks and acts like the strongest wall near it. If it isn't near any wall it will look and act like the strongest wall in the composition.

What do you think about it? Does the trap look overpowered or it needs some improvements?