Alpha test: OK on Linux, too many glitches on Windows

Unexpected results of alpha-test: it doesn't work properly on Windows. There are glitches, important things do not appear, and... it's unplayable. I thought that .wasm ought to work on any machine as long as the browser is compatible... 

That's a very precious discovery, but... because of this I only had limited feedback on the game...

Is it an SDL problem or an emcc/compilation problem?

What I know:

1. Glitches are the same on any windows machine 
2. On dual boot, it works on ubuntu or arch but not on windows.  from 1 and 2 at least I can tell that's not a graphic card problem
3. In game it affects the 2/3 first fields that became black, but not the others if the player managed to pass through them blindly.  as they are the fields with the less tiles (less information), the problem is probably not because of too much computation to do and anyway, it runs fast
4. for only one of the other animation I have flickering, with colors of objects mismatched (very weird)

DONE

• Fields generation
• Obstacles generation
• Player 2D movement
• Interaction player / obstacle 
  • blocked
  • destroy
  • push
• Test: is it fun to play?? at least, it works. And yeah, with 1975 standards, its probably impressive and fun xD
• Inter-field space generation (change of strategy, extended array with entry and exit field)
• Obstacles generation animation
• Import some real data
• Welcome Menu
• Sound
• Some "animations"

TODO

From high to low priority.

• Make it work on Windows!!
• Understand that the player is stuck.? Impossible
• Time, score
• Translations
• Test: what is needed for more fun?
  • special events? new powers?
  • Is it easy / fast / worth to code?
•  Interaction player / obstacle 
  • drag (useless?)
• Aesthetic (-- ... hum ...) 
  • Sprites instead of uni-color tiles
  • uni-color maybe better than ugly sprites ;)