It would be nice to get a warning when something isn't sufficient for a breeding (den space, lion(ess) food/energy/mood).

I seem to remember being able to breed with a full den, and also not using up a breeding when your lion or lioness wasn't prepared. I might be wrong about that, but even so, I'd really like to see some sort of warning, or a failure to use a breeding with an error, instead of using up your chance.

Edit: I see now that the lionesses that failed are still in heat, but on the page after the failed try it said they can't breed again so soon and the 'will be in heat for x days' message was gone. That really threw me off. So I suppose now I'd suggest changing the way these errors are presented to be more clear.