Develop iPhone Game - Art assets provided

I am looking for an iOS developer to create a game reminiscent in both mechanics and fluidity to the popular "Tiny Wings" game. This will be a mobile game intended to drive brand-recognition for a US-based toy and candy company, but it should also be fun and addictive. Though we are not attempting to compete with the top dogs in mobile, we ARE looking for a way to engage with our customers and allow them to interact in a new way with our product. We will provide Art Assets in one of two ways, depending on which seems more plausible depending on the selected bid. Either the bidder will create very simple graphics with which to make the game and then send us the spritesheet and additional images as an asset template from which to create our branded graphics, -OR- the bidder will give us a very specific asset list with dimensions for all assets and we will create them from that list. As for the required work, we will need at minimum: 1) an opening splash screen 2) a main menu including: -character selection -level selection -high scores list (based on distance traveled) -a link to our brand's website 3) 15 levels Additional design and functionality my arise, including: 1) In-app purchases (characters, themes, power-ups, etc.) 2) Facebook et. al. connect/share/like options 3) Themes to pitch the game for different seasons/holidays/events But those are not a part of this bid. Though the Project is currently set up as a Fixed Price, we would be open to discussing an Hourly budget instead. Before selecting a bidder, I would like to talk a bit about estimated development time. Thank you for reading.