I made a small update to this early this morning – the logic for colouring the heated pieces has changed to use a trivial tone mapping HDR compression rather than my custom hack that I had in place previously. This means the colours look more vivid. It also changed the game play slight as colder items are more easily seen than they were before. (Specifically the visibility threshold has dropped from about 1800K to 1000K.) So I am using this as an excuse to try a new set of default parameters out.
Maybe next weekend I will take a look at adding radiation heat transfer to the game. However I do think it will need to be a small component compared to conduction or the gameplay will be significantly impaired. I mainly want really hot pieces to cause non-touching but nearby cold pieces to start to glow, only at short range. I do not want the top layer of locked in pieces to go cold while you try to drop a piece down on them. (Or the dropping piece to go cold before it even gets to the bottom.)