User blog comment:Luvdwayulie/IMPORTANT: Grammar Fix + Difficulty Name Issues/@comment-3225604-20140311123553/@comment-5665767-20140311125025

"When" is used when we are certain of something has happened, is happening or will happen. In this case, it's not certain that we have moves left every time. "If", on the other hand is used when we are not certain of something has happened, is happening or will happen. In this case, it's a better option to use "if".

Source: http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv179.shtml

But, I do get your point for this. So, it's half-half. But I think most levels have been changed to "if" lol.