Drop tiles into the grid. Try to make adjacent tiles (columns or rows) add up to the required value. When you do the tiles in that group change colour, until eventually some will turn red. Make a group with a red tile and it will explode, causing the tiles above to drop down, leading to combos and big points!
Play in basic (try and make a group equaling 9), timed (drop tiles under pressure) or arcade (the quality of your play leads to power-ups).
This is v1.3 and I believe the final version. Thanks for the support from everyone on Newgrounds! For those looking for older versions of DropSum here, I deleted them - they didn't get blammed!
Stuff in the new version:
Prettier graphics and a background image, which changes on special days and monthly.
You can only collect 20 stars now.