Plants vs. Zombies - what kind of tips do you have?

You guys turned me onto this game. I made it through the first time to the video. man, the roof was horrific, Learned the balls of fire can be blown up with ice and the ice can be blown up with fire.

My fave weapons are the squash, potato bomb and the pea shooter that goes in both directions.

i swear I have stayed up 2 entire nights playing this game. On level 3 again. The fog. with balloon zombie. What do you know??