That was fun although it got kind of repetitive after a while since enemies just walked in a straight line towards the portal, and flying through stronger ones felt spongey and unsatisfying since they took multiple hits to kill.
This is a cool idea and has a lot of potential but you might need to rethink the goal of the game. I think the focus should be on getting as many kills as possible as opposed to protecting some portal.
Maybe have the arrow lose momentum over time as it flies but gain momentum as it kills enemies.
edit: Oh and I forgot to mention that the game didn’t work in Firefox