From publisher blurb: Spacecraft Builder is a Stellar Wind Player’s Aid. Player’s Aids are small works that provide useful tools for both GMs and players. This aid consists of two spreadsheets that do all the heavy lifting for you when building spacecraft for the second edition rules. One spreadsheet is in Excel format for Windows users who have Excel 2007 or later and the other is in Numbers format for Mac users who have iWork 09 or later. The Excel spreadsheet has basic formatting and performs all the required calculations for size, cost, downpayment, etc. based on your selections. You can then use the final information to fill out your Spacecraft Data Record sheet. The Numbers version fills out a Spacecraft Data Record for you as you work through the spreadsheet. When finished, you can copy and paste the resulting data record into Preview for printing. The Numbers version WILL NOT work on Numbers for iOS.