Although visuals are not the best and it clearly doesn't have any sounds, you had everything a platformer should have and you implemented all the core mechanics you needed -- use of gravity, smooth character controls, shootings, etc., and they worked perfectly.
As a programmer/designer you've definitely achieved your goal, and if we were in a team this would be a totally acceptable prototype to show to your art/sound team, and it definitely has potentials to be something greater.