In part, their strategy to accomplish this comes from simply reversing the balance of roles. They aim for a mix of about 70% in the stealthy sniper role with the remaining 30% in guns-blazing firefights. This formula also allows them to interweave the two roles with back-and-forth play where a level gets played from both points of view: first as the sniper providing overwatch and covering fire, and then coming back as the assault soldier in the thick of the fire being saved by the sniper.
They also treat the sniper's mission as more than just pulling the trigger. Getting into position without raising alarms plays like other stealth games with different cover types providing their own degree of concealment. Not all missions are straight assassinations either. Sniping also gets used as a tactical method to infiltrate enemy positions to steal data or perform other covert ops.
And when the bullets fly, Sniper gets down to details taking into account the shooter's heart rate, distance to target, and wind drift. For a completely different sort of experience, though, there's a more shooting gallery type of mode that factors all that in and puts a pip in the crosshairs showing where the bullet will actually strike. I can see appeal to both ways of playing Sniper: one for its increased sense of satisfaction for hitting the shot -- complete with bullet chase cam to the perfect strike; the other for its simple pleasure of hitting a steady stream of headshots. We'll see how well it accomplishes either soon enough. Sniper is due out this spring on PC and 360.