Not the dev but I just played it and here's what I got.
Yes it seems to be tuned to AZERTY keyboards (which i know because it's the one we use in France). On windows you can switch to different keyboards but you might need to download it.
About the absorbing functionality it took me a while to understand: when 2 balls are in the same spot you can press "down" with both balls to merge into one ball with resulting color the mixed color. For instance blue + yellow = green, then you can pass green walls, then you can switch back to 2 separate balls