v0.1.7

Updates:

• Added the beginnings of an InventoryManager that will interface with the Port screen, keeping track of crystals collected, and credits earned. 
• Amounts of crystals collected now appear correctly in the Port screen.
• The default amount of 500 crystals appear in the Port's inventory to purchase (this will vary depending on supply and demand later).
• Added ability to save Inventory amounts by pressing the 'Insert' key. This will save your crystals and credits so when you return to the game, they will automatically be reloaded. Saves are not automatic (yet).
• Pressing 'Delete' key will result in the game resetting your crystals and credits to 0.
• Buy/Sell/Refuel/Repair buttons operate properly on the Port screen (Port credits do not go down or up currently). 
• Sell Green for 50 / Yellow for 100. Buy (from port) Green for 100 / Yellow for 200. Refuel costs 500 (currently does nothing but reduce your credits. Use only for 'simulated' purposes atm. Repair costs 1000 (also does nothing except reduce your credits.. probably just dont use this yet).

Thoughts/Observations:

• A game state system will likely be necessary as the additional screens get added that will determine what screens you can get to from which states. IE: After getting into the port, if you want to get into a different screen within the port system (not yet decided or figured out, but it certainly could be possible I might have to break the UI up into more digestible parts), you need to be in the 'InPort' state. You can't just press U to jump from the 'Flying' state into the Ship Upgrade page.
• Once the game is further along, save progress will likely just happen semi-automatically/via the pause screen and deleting of saves will be managed in the main menu.
• This was a pretty substantial update for me so far, adding the buy/sell feature and inventory management  is the beginning of some awesome stuff. I already know I'll have to refactor some of the UI management code but the main code for buying/selling is set up pretty well to allow for new crystals/other things to be added.
• So far 'Sell 1' and 'Buy 1' are the only options available. I am working on improving that design so it works well with changing small and large amounts.