Look good, it be a good arcade but the collition with the high ground were the aliens are it's weird its displaced, the characther is too slow as it can do anythinh more tha walk, feel that slugish it's a bad thing even when it's good balanced, don't feel unfair, but you not enjoy it eithers it's simply meh.
Either give it a more frenetic movement or give the characther more actions to do like roll to move fast, put temporary shields or somthing to return the shots to stun the aliens, with a weapon or a shield.