Situation where player doesn't roll towers during pre-game is not handled

[phatnguyentan]

[Kvel2D]

There is a 3 minute timer before first wave, you are supposed to research elements and roll towers before that 3 minute timer expires.
The problem is that the game doesn't handle the situation of "player does nothing for 3 minutes" correctly and removes the roll towers button when the game starts.

[Kvel2D]

I made the "roll towers" button stay around if player fails to use it before first wave. Also, there's a warning message which suggests to the player to restart.

[phatnguyentan]

I can roll tower and play, but it's make me confusing, should we have default towers instead of roll towers