On level 35 near the entrance, Tux is surrounded by negative (dark) light radius.

Screenshot attached.

r4892

Looks like some kind of overflow. Fluzz, would you please investigate this? It's
your area more than mine!

I don't think this is "important" though, resetting to "bug".

I rather think that the light values of level 35 are wrongly set.
I'll check them.

That's really strange. There is no such bug in any other levels, with same light
configuration...

I was able to reproduce the bug on level 24 as well, with some tricks.

Change the light properties of the level to ambient 12 and bonus 9.

Place a sign somewhere.
Place another obstacle which  (lamp for example) nearby.

Since only obstacles near tux are computed, this bug will only be visible within
certain range near the sign.

You must be in eye-contact with the sign. Otherwise there will be no bug.

When you now are near the sign, there is no other obstacle blocking the path
('view') and you are in the light radius of another obstacle, this black aura
will appear around tux.
As soon as the sign obstacle isn't computed anymore, the light radius will be
back to normal-

modified SC attached.

Note: when replacing the sign with an animated sign, the dark aura only shows up
while the sign is turned "on" (emits light).

What we've found until now: the bug appears because the light emitted by a sign
(5) is lower than the ambient light of the level (9).

I now have to investigate the code, to understand why...

That's strange, indeed. The bug may appear with my recent changes in this area.

Fixed in svn r4896