The Sentinel in 2D

When reading some stuff about one of my old C64 favorites "The Sentinel", I wondered if something similar would be possible for the 2600. Since 3D was sure impossible it had to be in 2D. Attached is a very preliminary result.You now watch the game top-down, your own position is at the bottom of the screen. Your sight is limited but you will be(!) able to rotate in 90° (maybe 45°) degree steps. For the heights, various colors are used, starting with dark magenta, then blue, cyan, green, yellow, orange up to bright red and finally white. So it will have only 8 heightm but that seems sufficient.Invisible areas (e.g. behind mountains) are black, unreachable areas will probably become gray (with a height matching brightness). The cursor color will(!) switch on those unreachable/invisible areas from green to red.The kernel has become pretty complex, jumping into RAM and back to (various!) ROM adresses. The game will definitely require a lot more than 128 bytes of RAM, especially because I want to write a landscape generator.Since I am going on holiday tomorrow, I thought this might be a good moment to share what I got so far.Biggest left problem so far: Calculating the visibilities of the squares.Source code attached.