Picnic Panic Tower Defence is a very complete flash tower defense game. Not only can you build ice, fire, poison and guard towers in Picnic Panic, you also have several upgrade options. The ability to sell your towers at 100% their value is absolutely vital to defeating the little critters. This allows you to build up a defense at the opening of the path. Then when the surviving insects get through you can fortify for a last stand.This game is pretty tough on the later levels.