I can't reproduce this - thought it might be if you have a tower selected when a new wave comes - but basically - you have a tower selected and wait for enough money to upgrade - when you hit 'U' sometimes it works - sometimes it doesn't - you have to click the tower again for the hot key to work

Also - I know I mentioned this before - but if 'Y' could stop de-selecting the tower - or even better just do an upgrade that would be fab.

Ya, I've had the issue happen to me too. I go to upgrade a tower (by pressing "U") and it doesn't do anything. i have to reselect the tower then press "U" again.

As of right now I am not sure how to reproduce the problem. If you ever figure that out, let me know and I can fix it easily. It's hard to fix it when I don't know it happens :(

I "could" make 'Y' upgrade also, but them people will want "I" to upgrade too, and "M" to send next wave early... :)

Yup, have that same issue too sometimes. Reselect is needed to be able to upgrade. I'll try to figure out when it happens.

I haven't tested any of these ideas, but all I know is the user must press a key/mouse button that (in the code) assumes they de-selected the tower.... yet it remains selected on the screen. So when you press the "u" key to upgrade the code has no idea what you are trying to upgrade cause it thinks nothing is selected.

Not sure what key or mouse press would cause that yet

I don't think it is that - I am 99% certain I have not pressed another key
In fact when I hit another key it deselects the tower which is even worse

I'm convinced it is a particular wave causing it or maybe killing a boss? When it does the animation for the power up?

Not only U, but while a tower is selected, i can't use "N" which I can't find out why either :s

Re: y I n etc. If they just did nothing and kept the tower selected would be good?

Well, when I am trying to upgrade while clicking a creep for my towers to aim at it, itd be nice if the N button worked while doing either but only works while clicking creep, and not while upgradeing or selecting a tower.

I have found out why the game sometimes doesn't allow you to upgrade/sell a tower when you have it selected... I haven't finished reading this, so i don't have the solution yet...

click here to read it

Ok, found the solution. not a bug with my code.... for a change :)

click here if you are interested