in the graphics world there are 2 accepted ways to treath transparantie.
The old way, but still used by a lot of applications. De left most bottom pixel is defined as the transparant collor. En de render engine will filter this color out.
Happy to say this is not how Construct does it.
True transparanty, as can be find in by instance .PNG files. Where the background is just transparant based on a mask.
Now well .GIF files still use both methodes. My gues is that he/she is using the first way.
Wich is (thx god) not compatible with construct.
In other words, it is not setting the colors defined by the first pixel in the bottom line as transparant. As he/she expected.
Hope she/she will try out the PNG's that i provided.