This was a very cute entry. Had you added some sounds and music to it and it would have been great. I think your levels were really thought out and you managed to convey the mechanics of the game quite well, so you actually did good design. In that regard, the only thing I would have changed is added that the blue character can crawl in the level where you're first supposed to use it. I did figure it out, but I wasn't sure for a while what to do.
Also, your last screen is just imposter syndrome. Like I said before, your levels conveyed the mechanics well and were fun. Give yourself more game design credit ;)