Adding to what 
ErekT said.
Doing this will reveal just how bad it can get:
The project has just this + platform behavior and 3 solid planes.
The square will keep randomly changing to black and white in Chrome and NW.js export.
On some NES games there's bits that fake transparency by having sprites flash on/off at 60fps.
Doing so on C2 is gonna reveal the random here and there long delta when the sprite holds on or off for 2 frames.