QUOTE(JuiceBug @ Aug 4 2006, 11:43 AM)
It will center on the leftmost uppermost marine...
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leftmost lowermost...
starcraft refers to unit first by their X-axis(left to right). when two units share the same x-value, their y-values(bottom to top) are then checked and compared. lower values are detected first.
note: i don't know if this is how starcraft technically works, but in most cases, thats how it practically works. the only situation this would be false in is when the units were placed in SCMD2(maybe SF too). in which case, units are detected by their unit placement number instead of location. lower numbers are detected first i think.