Currently the progress of a Building is shown in the Right Panel in very small and inconspicuous script. When trying to decide how to contribute extra cards to Accelerate the building, I completely ignored it, as it was hard to notice. This meant, that despite the clear prompt Accelerate building, I ended up being unable to add cards to the completion, even though i clicked on the prompt, and then some cards. This seems to have been because, for obvious reasons, I had to then click on the building I was adding the accelerating cards to (because there might be more than one being built).
While this general mechanism is obviously workable, it is confusing, and especially if you don't spot the small building progress script, you will be screwed and have to wait for it to complete without any acceleration. So my suggestion would be that immediately clicking on Accelerate, a prompt appears in a box, asking you to confirm which building you want to add cards to, and then letting you select some.
A second possibly easier fix could be to make the Building Progress button much more conspicuous in some way.
While this general mechanism is obviously workable, it is confusing, and especially if you don't spot the small building progress script, you will be screwed and have to wait for it to complete without any acceleration. So my suggestion would be that immediately clicking on Accelerate, a prompt appears in a box, asking you to confirm which building you want to add cards to, and then letting you select some.
A second possibly easier fix could be to make the Building Progress button much more conspicuous in some way.