Cool idea and implementation of it. I like the style and the music, feels very polished.
At some times the dialogue was restricting my vision I found out about the E key later. And the learning curve could be flatter, from the second level on it gets fast and mean really quick. Sometimes blocks really blocked the flamethrowers and sometimes not, I didn't quite find out what the rule was there.
What bugged me most were the short period of time until an unused block disappears (or the long time until the new one appears) often the first disappeared right when the second one was appearing, that was frustrating. Maybe you cheat a little there and hold one block longer when a new one is appearing next to it -or change the times for (dis-)appearance- to make it feel right for the player.
It didn't help, that the position of where the block will appear relatively to the mouse cursor didn't feel right. That did increase the time to "aim".
Overall a great game, that needs some fine tuning. You should definitely follow up on this one.