Play it on Chrome if you want a chance at the highest scores. (Check my score for proof I am definitely qualified to make this statement -- at time of writing this review, the #1 score)
This game is hardware and browser dependent in that it very well can lag up or start lagging or becoming less responsive (even from the start) and yes this will kill you. Minus a star for that.
For best results, play on the very best computer you can (best RAM, best CPU, best GPU), and additionally play it in Chrome browser. Too much lag in Firefox even with a decent machine.