The risk reward mechanic of collecting more souls for extra XP was smart and pushed me to play harder! The crunchy effects of biting, the kills, and the juicy level ups were all very effective and punchy.
I had a couple issues though. 100 souls is a pretty big goal, perhaps a 25% too big in my opinion. Cerberus himself could have had some better animations, as he's the star- I though all the enemies pixel art was pretty darn good though.
My biggest issue was that on the web, holding right click to move fast was a poor choice as it seems that on Firefox it interacts with some other keypress (WASD or left click, not sure) to open contextual menus. I also had an issue where when I entered a new screen, if I was holding left click, I would bite once and then stop, which was a small hiccup in the flow of the game, but led to me losing all my souls multiple times as the enemies made it through my chomp-wall during the lapse.
The other issue was that enemies immediately do contact damage after returning to their bodies. So my last second dashes to pick up their souls were 50/50 chances that I would lose all my souls again trying to stop them. I think they should have flashed or played an audio cue as they were regenerating, and perhaps come back partially transparent for 1 second or something during which they can't damage the player to add a small buffer.
I enjoyed crunching on enemies and I liked your take on delivery. At first, I thought it wasn't very on-theme, but as I played, it became obvious that I was playing fetch with the souls and the "delivery" portion of the game was strong! I almost wish holding more souls gave you an additional benefit like greater speed or attack speed to further encourage the icarus-flight of risk/vs reward.