Floating target values in action thriller games

Action thrillers are packed with high levels of anticipation, uncertainty, surprise, anxiety and terror, so it sucks to know you character disarmed the trap before opening the case! Knowing my character succeeded the roll kills all uncertainty and smothers any anxiety and fear of actually going ahead and opening it. On the other hand I can't just open it blindly, I must know if I succeeded. There has to be a middle ground between being totally uncertain and somehow know I did a good job at disarming it. It is here that floating target values and split dice mechanics come into play.

Floating target value is a term I use to refer to cases when a roll needs to beat another roll. The target value will fall within a range and the player doesn't know this until the GM rolls. Thus the term split dice mechanics. The player rolls dice, the GM rolls dice and the outcome is successful if the player's dices beat the GM's, but the player doesn't know what the GM rolled! The player may know their roll was good or bad, but can't be certain of its outcome without knowing the GM's roll, and so the tension builds.

I'd like to make a clarification that has been pointed out by many readers after I posted this article. Floating target differs from opposing die rolls in that the later is a subset of the former. Opposing die rolls require one roll to be above the other. A floating target can also be a proximity value,  for example 2 below or above the value rolled by the GM. This makes it harder to guess! From the previous example if I roll 2d6, in a roll equal or over opposing mechanism a 10 is pretty good and a 12 is unbeatable; in a proximity roll within 2 anything goes, a 4 is good if the GM rolled 2,3,4,5 or 6. If the GM rolls an 8 then the values for me to win would be 6,7,8,9 or 10, a truly floating target!

The Saints & Sinners skill mechanics is based on opposing die rolls. Characters have a skill level that determines which dice to roll and tasks in turn have their difficulty rating and their corresponding set of dice. The player rolls, the GM rolls and the outcome is resolved based on the difference, but only the GM has both parts of the puzzle and can thus leave the player guessing. Did I type the correct stargate coordinates? Was the trap disarmed? Was the bomb defused? Did I hit the monster behind the wall? Did my machine gun fire hit anything in the bush behind the tree line? Who moves in to investigate? Who opens the door? Who goes beyond the event horizon first?

Drawback? Well it requires a bit more rolling and comparing, after all nothing beats rolling a d20 and seeing if it beats a target value. Pros? When it comes to thrill, nothing beats not being certain of the outcome of a dangerous task such as disarming a bomb! No matter how much players might say they don't metagame, they will, even a tiny little itsy bit. This way the GM gets to keep the result secret without depriving the players of their opportunity to roll for their character. Personally, its worth the overhead! What do you thing? How do you keep your players on their toes?