Thanks very much for the great suggestions uscftigerprowl, I will definitely start implementing some of these.
About point 5. You should be able to type in the moves in modes 3 and 4 now that the board has disappeared. Perhaps I should offer this form of input in all modes just for the sake of consistency.
By the way, I certainly don't intend for anyone to have to pay to download. The optional payment is just something that the hosting site offers by default.
Hi, I've been working on a little chess app to help train blindfold play (which should hopefully rub off on your ability to calculate long lines in regular play too).
The app is still very much a work in progress, but the idea is that you face off against my (currently not-super-impressive) computer opponent in four modes of increasing difficulty. In the first mode, for example, the board is visible, but the piece are only drawn every couple of moves. By the final level, the board and pieces have been totally removed and you have to keep the entire game in your head. (Moves are entered algebraicly at this point).
If you'd like to give it a shot, it's available freely for mac pc and linux at this link: http://sebastian.itch.io/blindfoldchess
All feedback is much appreciated. Hope you enjoy! (also feel free to share your blindfold games here; a recent update allows you to copy the pgn once the game is over - just enter review mode to get the option).