Yup Sascha is right here, this is a bug. The two left steel walls turn to normal walls like this.....
*edit*
I thought I'd try to blow it up to see if it really was a normal wall (and not just a graphic glitch), and I found an even worse bug.........Steel grow walls aren't even indestructible!
I think the reason why there appears a normal wall is this:
Holger, could it be you used the same code for the growing steel walls as for the normal growing walls?
I mean, the walls are not destructable (okay, now they are) and so they behave like normal growing walls.
I've not got asny knowledge about programming games, but could it be that the normal growing walls knew a special case: If two gr. walls hit there's a specific funktion which solves that point? I mean, when two gr. walls hit, which one should go on growing while the other has to stop? Is there a kind of priority that rules?
That element, that rules that case (if there is, I just said I'm not a professor) has been forgotten at making new graphics for it.
Everything is prioritized by the scanline (left+top 1st, then right+bottom) so any grow wall above or to the left of another will finish first. You can change this though by setting engine actions to reverse.
> I think the reason why there appears a normal wall is this:
No, it's just simply as I wrote: In the current release version, growing steel wall left behind normal wall. Try it! They don't have to hit each others like in your level sketch -- just put one single element in a test level and let it grow. Go away so that the steel wall disappears from the visible area and go back -- voila! (The graphics are updated correctly when growing, but not the game element in the playfield array, so you can see it when its redrawn from the playfield data.) Instead, just bomb away every "middle" elements of growing steel walls to see the effect!