That is hard. Fair, but hard. Only qualm is that pressing a number only toggles that block on. If it is already on, nothing happens. This makes it a bit harder to toggle blocks in air, considering you have one chance and you are focusing on the block you need to toggle, and therefore press that button, changing nothing and causing your untimely and quite unfortunate death.
Using the mouse is an alternative where the blocks are toggled 1-2-3 with the left mouse button and 3-2-1 with the right mouse button. It also avoids a control issue called keyboard ghosting that affects some keyboards.
fantastic level design
yeah love it
Neat! The gameplay is very smooth and fun and I've enjoyed the increasing difficulty and complexity of the levels! I'm definitely gonna get all of those medals ;P
By the way, one thing totally caught me off-guard. I've noticed that in the software section to the left you have "Inkscape" added. Did you only use Inkscape to make this game's art? If yes, then I'm really impressed, I use it on a day to day basis and didn't know you could make full games using it! ;D