Its a good game but lacks the substance to maintain one's interest and can lead to some very frustrating circumstances.
You can chop wood, mine copper, kill blobs of goo and build yourself a house(s) etc. This is all well and good until these things have been accomplished...sure later on you can build more buildings out of stone, copper blocks etc. and kill zombies and flying eyeballs even bosses later one, but here is where I personally began to lose interest in the game.
The fact that to get to a boss means you have to trek for miles in a certain direction, climbing hills, avoiding massive holes and deep water, these all kinda zapped the energy out of me. This especially true when I would time a jump wrong and land in a dark pit with no source of light and no way of knowing how to climb all the way back up. Stumbling on in the dark is my only option until some mob kills me depriving me of some coin and items (depending upon difficulty).
Now this can probably be put down to poor preparation which granted is probably a valid point. However, the amount of items found when exploring dungeons, mining underground and killing mobs, away from the safety of 'home' sometimes means you have to toss out items to make room for more important one's.
On more than one occasion I would toss out my torches and then regret doing so moments later when on the return trip I land in one of the ever present black holes, either dying due to the huge drop or landing in a mob 'nest' and murdered.
All of the above might be just my pure incompetence but the frequency at which I died when carrying rare items I found to be a bit suspicious.
On the plus side you can craft/buy armor, weapons and items which might boost your jump height or maybe increase your movement/attack speed. This creates a collection system by which users seek to collect an entire set which might grant a movement or damage increase. Hearts and stars are also collectibles increasing your over all health and manna respectively (you need something like 8 to12 stars to craft another manna slot).
Over all I consider the game to be pretty good diversion for those willing to pay the $15 for it. I, however, haven't played the game since the end of 2011 spending my time in another sandbox game world called Minecraft. A game which though lacks epic looking armour and boss fights (the exception being the enderdragon) provides a much more entertaining experience.