It's parallax layers, but different

Here a quick explanation how the pseudo 3D effect in the game works using only 2D rendering.
pseudo3D explained

Parallax planes, but different
1. early development, everything flat, only lines and squares
2. first attempt to draw in pseudo 3D, didn't look great
3. second attempt, much better looking, how?
4. it's done using layers, e.g. guard consists of 7 layers
5. also the console, door opener and treasure are rendered with layers: 3 layers were enough
6. walls need a different technique: pygame-ce has no method to draw textured polygons. So the walls are drawn line by line, each adjusted in place and length
7. showing the layers of the robots.
The layers are displaced like a parallax layer, but in front instead of behind the main layer as usual.

Here some screenshot how it looks in the game:

screenshots of the game