Managed to finish on first attempt with a score of 8784.

Some quick feedback;

• When I tried it on my main browser (Vivaldi), after selecting first upgrade the game stayed frozen. Had to switch to EDGE to play it properly. It would be nice to have downloadable version to avoid that
• I felt it was too easy, as I won on first attempt. may want to adjust the balance
• Skulls weren't really a threat due to how slowly they change direction. If they perhaps exploded on death, then they'd be something far more dangerous to deal with
  
• The weapon sound quickly got irritating. If you're not already, try varying it's pitch.
• The weapon felt weak due to it's sound, animation and lack of enemy hit reaction (like the humanoids don't flinch in pain)
• The exp crystals would sometimes orbit around player, may want to put some dampening on them
• It'd have been nice to have UI indicator of weapon stats, could perhaps show it on upgrade screen. Sometimes it felt like upgrade didn't do anything and I wasn't sure if that's cause I'd maxed out a stat or if the increase was small.
• Player can jump even when not on the ground, thus can 'fly'.
• Combat could use some more depth, like alternate attacks (eg grenade or AoE attack) and enemies that have special requirements to kill (ex. shoot weak point, specific damage type). Could also have special enemy types like one that buffs nearby allies making it a priority.