It's good, but I find that the lack of a lead-in time when "Getting Back to Work" results in frustration. Because sometimes you respawn with enemies around/on top of you; so before you even have a chance to click away you've lost 1, 2, 4 hearts. A "Ready Set Go" at least would be nice so I could be moving around before the heroes spawn.
Another suggestion would be to set up game failure on a 4/4 warnings results in 20 levels lost, then 30, then 40, then 50. Game would then be over when levels lost is greater than your current level (i.e. losing a fourth time when level 45). Any of the abilities you had gained would carry over after losing levels. For me, that would extend the time I'm willing to spend on this and make me feel like I have a fighting chance.
All in all, well deserving of its awards. Congratulations!