A Few Extra Plot and Image Points

I envisage a sea cave that the boat can sail into, but only when the portcullis across its entrance has been raised. So the player is at a land entrance to the cave, and can raise the gate from there, but the dock in the cave is only reachable by the boat sailing in.

Also, I started to devise a new spiral staircase function where the steps were not connected at the centre. I realised yesterday I could use an existing spiral stair function, and cut the centre out of it by differencing with a cylinder. I'd still have to add vertical struts on the edges for realism - a staircase can't just hang in the air - but the main job will be done.

Fan animation. I observed how a fan opens. The rearmost blade of the fan stays still, and only the top blade is showing. The top blade flips out, pulling the next and the next and so on.

I suspect the best way to create the images for this in povray would be in reverse. Start with the open fan as an array of blades, coat the array with the image, then for subsequent frames, pull the top blade back over the one underneath it, then pull them both back over the third, and so on, until the fan is closed. I'm not entirely sure this is possible, though.