[hercooles]

If I place a spot light behind a relative sprite and then make the sprite one sided, so that you can´t see it from the place of the spot light, will the spot light cast a light through this sprite or will it cast a shadow of the sprite?

[High Treason]

It often casts a light right through it... If you wish to make shadows try entering 2D mode and hitting F8 on the sprite, select "Owner" in the dialog at the bottom of the screen and press Enter - I assume you know how this works if you can place lights already, anyway, set "Owner" to the tile number that you want to use as a shadow, press ESC when done.

[Plagman]

If the light can see through the sprite, it won't cast a shadow. That's how the grating projection is achieve in E1L1, among other things.