This really is a great game.  When it first came out, I was burned out on real-time strategy games, having played Warcraft 2 to death.  I played the first 15 Starcraft missions, then gave up on it.  Partly, my nerves were  shot:  RTS does that to it.  It's a very frenetic type of game, with lots  of rapid clicking, scrolling around on the map, trying to keep it all under  control.  You have to hold a lot of stuff in your short term memory, and  (in the harder levels) the constant onslaught of enemy attacks tends to  make you forget what you were trying to do.  --This is one down side of RTS  games in general, and Starcraft is no exception in this regard.