This is cool and well made, especially given it was made in Scratch, well done! However, I must unfortunately criticize the gameplay. In such "destruction chaos" type games, it's generally good to give the player as much freedom as possible, have things fly around the screen, one thing breaking another, fire spreading from object to object, things like that.
I didn't like how restrictive the object placement was (one pixel of overlap and you get nuh-uh'd) – I think you could at least made the object glow red when you can't place it in a spot, and don't make it disappear when I click on an invalid position, but just allow me to place it again immediately. As others have pointed out, the torch is a bit counterintuitive – it only makes fires bigger instead of creating new ones, which may be a tad pointless? I mean, fires usually get bigger on their own, don't they?
Finally, there's some kind of balancing issue. While it's definitely possible to beat all difficulties with the items you're given, it's never really the "complete chaos" kind of fun. It's more of a "strategically place the few limited resources you're given" kind of fun. Which can certainly be fun, I mean look at PvZ no sunflower challenges for example, but I think that's not what you were going for. Make sure your game design is in line with your vision for the game.