 Within the week , they had a working game written in Adobe Flash 's ActionScript 2 . The two agreed to complete it out as a game they could release on Steam though with no expectations of sales . Completion of the game from the prototype to the finished state took about 3 months with part @-@ time development . During this time , they discovered there were several limitations on the size and scope of both Flash and ActionScript that limited how much they could do with the game , but continued to use the tools as to release the title . McMillen said that because they were not worried about sales , they were able to work with Valve to release the game without fears of censorship or having to seek an ESRB rating . Releasing through Steam also enabled them to update the game freely , several times on its initial release , an aspect that they could not do with other consoles without significant cost to themselves . They did release without significant end @-@ user testing , as it would have taken several hundreds of users to go through all the various combinations of items that a player could collect , and McMillen recognized they had released the title with their buyers being playtesters for them . A week after the Steam release , McMillen released a demo version via the website Newgrounds . Merge Games produced a physical edition that included the game , soundtrack , and a poster , for stores in the United Kingdom in 2012 . 
