You're trapped inside a tower and want to get out. You can jump from left to right and back and every jump takes you up a little bit further. While you rest against the wall though, you keep sliding back down. After a few meters you cross a laser beam and that activates a ray that will kill you if you touch it. And the ray follows you upwards. Make sure that you don't touch the sharp bits of the wall, you can't handle them well, either.
You can play this with the escape or up key.