I first downloaded this after I saw a link to the game's GMC topic. The name 'An Untitled Story' sounds like the creator was just too lazy to make up a name, but the creator of this game (Matt Thorson
/'Yo Mamas Mama' - creator of the notoriously difficult 'Jumper' series of platformers) showed just how much detail he is capable of putting into a game.
His site says "you begin as an egg in your nest, and the rest is up to you to figure out". This exploration/platform game has 18 bosses, and a massive worldmap. It has multiple difficulty levels that range from 'Simple' to 'Insanity', and in no way should this be considered an easy game. Later in the game, the complex platforming challenges, often involving split-second timing, become challenging enough to make you pull out your hair, but they won't stop you playing.
My only problem with this game is the low number of savepoints. Annoyingly, there are often no savepoints for a while before bosses, so every time you lose to the boss, you have to go through long stretches of platforming to get back there. Also, there are no health restoring items other than savepoints, and a health refill after the end of a boss. You do get 10hp for every heart (which increases your maximum health) you get, but with enemies and traps regularly doing 100 or more damage, these don't help much.
If you want to see what this game is like, I would recommend the Lets Play