Nicely done, however, two problems:
1> No in-game instructions. Sure, you can get away with it here, but some game sites that this might be posted on might not have a text box for instructions, leaving players confused.
2> Not so sure this was intintional (sp?) : right as the overlaying shape appears, highlighting what you just destroyed, you can turn the board still, with all the peices actively falling as you turn, making combos much easier.
Gets really hard, but amusing, shortly after the max # of atoms increase. A hint to people: Make the old atoms fall onto the new atoms and chain reactions will get much easier.