Thank you for the interesting feedback! We agree on all the points you mentioned.
It would be indeed interesting to had an effect on the character when getting hit, because sometimes it's hard to hear the sound effect. We also thought that the score and the timer was missing while playing the game.
We agree for the scales, but it is also important to reduce the amount of glowing effects to help the user indentifying the enemies mechanics. So we need to find the best trade-off for that. We think that adding an outline would be a great idea.
Thank you for noticing us the rendering issue! And thank you again for playing our game!