Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Developer(s) | Release date | Required OS | Genre | Type |
| --- | --- | --- | --- | --- |
| Robot Entertainment , Gas Powered Games | August 16, 2011 | Windows | MMORTS | 3D |
| EA Games | 2009 | Windows | First-person shooter | 3D |
| Stunlock Studios | 2011 | Windows | MOBA | 3D |
| THQ | 2010-2011 | Windows | Real-time strategy | 3D |
| Novel, Inc. | 2011 | Windows | MMORPG | 2D |
| Masthead Studios | 2013 | Windows | Third-person shooter | 3D |
| Riot Games | 2008-2011 | Windows , OS X | MOBA | 3D |
| Valve Corporation | 2007 | Windows , OS X , Linux | First-person shooter | 3D |
Question:
What operating system was needed for 2D games?
Answer:
Windows