Why Does This Puzzle Seem Confusing?

[Adjoint]

Am I getting dumb for some reason or is this a good puzzle?
PF friends! What am I missing here?
Really, from where did that empty block come?

https://xgwwxq.by3301.livefilestore.com/y2mLyb0TiTKVjKIyM-YhPhH8eOUBpyahkjUp-JGHbYtGwUOUhaUCI8-nQbCiUgUR2JcwIsHxUVDu0Rc1Z9NuPIDyDiCORi9AMRbJ0afq0ZD3iFSO_bAKRzxuWL5O58DG0R5/Illusion008.jpg?psid=1

 

[CAF123]

Hi Adjoint,
Look at (I.e use a ruler or calculate) the slopes of the green and red triangles. It is more of an illusion to begin with.

 

[Enigman]

Solution:

Spoiler

The triangles are not really triangles. In the first pic. the 'hypotenuse' is bent inwards, while in the second it is bent outwards. Try Sam Loyd's dissection puzzle after this.

 

[Adjoint]

Okey, I got this finally. Really, its more of an illusion than a puzzle.