I timed it. First part took about 6:20 where as the first level of Super C only takes about 2:00. 6 Mins might not be long for a regular platformer but for something as fast paced as a contra game, 6 minutes is a long time.
Few other things I noticed:
-The marks for missiles that come down could be a lot clearer. I'm not sure if this is currently the case, but it didn't seem like they display on the top layer, perhaps that's just because they're blending in, but being on top might help.
-Lives should really reset between sections. RN I'm just killing myself to reset.
-Speaking of lives, it seems that getting score gives lives, but it might be more meaningful if there was an indicator of how much score you need between lives.