Yeah, I had to ponder the bird -vs- ground input box for a moment. I decided to allow simultaneous input. and once you get one of them CORRECT then it would clear the other answer box (because e.g. you solved 3x4 = 12 for the bird, but the next one on the ground is 1+2 and you don't want a 12 in that box still)
That created a bug of its own - if you solved e.g. 1x1=1 on the ground on "accident" because you were looking at the bird in the air with a "9 + 1 = (10)" solution, then after you inadvertently solved the ground equation, it reset the bird puzzle. So you would press 0 to think you were entering a 10, but now the input had only a 0. The solution right now is to preserve the work-in-progress answer as long as the current answer is correct (substring match).