Actually quite Good
Put in some difficulty settings, add longer time per setting along with adding even more types of timers to click on each with a different effect, try to have some what of a storyline if possible but it probably wouldnt work, good to see your putting out a new mine-field because this premise has a long road ahead and if you can do this right, you can have one of the best reaction-time games created in a long time.
1.Add on more time to each green timer
2.Add in different kinds, like an invincibility for 3 seconds or a clear the screen of bombs type.
3.Add the ability of difficulty settings with each difficulty giving you less time per bomb.
4.Create different game types like see how many oyu can clear off the board rather than having reseting the timer have the bombs come faster and when you click on them the bomb is destroyed but you have to destroy the bomb in that time limit with many more bombs respawning or being created.