Game Design #37: The Better the Hit, the Better the Damage - Managed Probability & Modifiers

I'm surprised how little this gets used.

STANDARD RULES:
Most often to resolve firing, a "to hit" roll is made.  Let's say 4+ on a d6.
Then a "to damage" roll is made.  Let's say it's also a 4+ on a d6. Or perhaps it's a roll to "save" damage done. It's just terminology - the effect is the same.
A pretty common, 40K-esque mechanic. I think Warlord Games needs to offer me a job!

However there is NO connection between the accuracy of the hit, and the damage done.  

It's the same with "criticals" in space and naval games.  A shot hits, then there is a separate roll for critical hits.  There is seldom any connection between how good or accurate the shot was and the % chance of scoring a critical.

This does not make much sense.  A well aimed shot should do more damage, or have a proportionately higher chance to do damage.

EXAMPLE #1:
I think I first noticed this with DP9's Silhouette system.  It's a little weird, but illustrates my point:

You roll 2d6 and pick the best one. (+/- ranged modifiers)
Your opponent rolls 2d6 and picks the best one too. (+/- defence modifiers)

Now you compare the difference (and this is the key word).  If the defender wins or ties, there is no effect. But if the attacker wins the difference is very important. 
Let's say the attacker rolled a 3, 5 and had a +2 modifier.  The best dice (5) plus the modifer (2) = 7   
The defender rolls a 2, 4 and has a +1 modifier. The best dice (3) plus the modifier (1) = 4

The difference between the rolls (7 - 3) is 3.  This is multiplied by the weapon's damage.  Let's say the damage is 4.  4 x 3 = 12.

As you can see, winning by a wide margin (say 3) does 12 damage.  Whereas hitting with only 1 to spare would do only 4 damage.  A better initial hit does proportionately more (or has a higher chance) to damage. 

EXAMPLE #2:
That may have been a bit confusing.  Here's a simpler example.

We need to roll a 4+ to hit in our "Standard Rules"  example above.  But we rolled a 6 instead.  The difference is 2.   Now, since it was such a great shot - much better than what we needed to hit the target - it probably it more likely to hit something vital.

Let's add the difference (+2) to the "to damage" roll.   We needed 4+ to damage in our "Standard Rules", right?    Sure, but when we roll the dice, we add the +2 difference to the dice roll.  So a d6 roll of '2' would not damage a target normally.  But when we add our +2 bonus for our great initial shot, it would be a hit!

We've just linked the quality of the shot to the amount of damage done. 

WHY DOES THIS MATTER?
It's common sense.    A easy, aimed shot at a point blank target is much likelier to inflict a deadly wound than a hopeful shot at long range.  The chance of a "headshot" when standing 1m from a target (with say a 80% hit chance)  would be much higher than a shot from 300 metres away (say a 10% hit chance).    In a space game, a starfighter which is skimming the Death Star's surface is likelier to hit a womp-rat sized hole than one firing from miles away.

It encourages sensible tactics.  If you have balanced your "to hit" roll, that is!  If you want to deliver the coup de grace, you may have to move close and set up a better probability shot to reliably do it.  Wargaming needs dice.  It needs that "uncertainty" - the chance of pulling off that one in a lifetime shot. However the probabilities should not be random.

MODIFIERS & MANAGED PROBABILITY
Paul of Man Cave fame recently asked me once what I have against "exploding d6s" (I was probably ranting about Aeronef/Firestorm Armada at the time).  Those games are the antithesis of managed probability. I'm going to make an extreme example:

Let's say a game needs '6's to hit.  If you roll a 6 you get another roll until you fail to roll one.
Each weapon has the same range.  
Once a shot hits, you need a '6' to destroy the target.
There are no modifiers to either roll.

As you can see, there is no real decisions for the players to make. Simply move their units into the mutual range and roll dice madly, hoping for a d6. A random 17% chance.

As you can see, there is no effective way to "manage" your chances.  Just chug dice and pray for d6s, which are disproportionately valuable.  All you can hope for is to concentrate your forces, and hope your opponent spreads his units out and attacks your forces one at a time, allowing you a better ratio of rolls.   Since all weapon ranges are similar, speed has no effect, you can guarantee this - simply clump your ships together and move at the speed of the slowest ship.

We need uncertainty - otherwise we'd have the boredom of chess - i.e. whoever had the turn automatically kills an opponent within range or something similar - but it needs to have a way to manage this uncertainty.

MOVEMENT & MANAGED PROBABILITY
Okay, here's an example of "dice to move."  This is something I have grudgingly become used to, but as a sport coach I find it jarring.  Kids don't suddenly run 100m in 10sec one day, then only 20m in 10sec the next (barring a broken leg).  It's about as sensible as dicing for the maximum possible range your weapon can shoot.  However time scales are flexible, and it does add "friction" to the game, and removes unrealistic precision.

Unpredictable Random
Every unit must roll a d20. The number it rolls on a d20 is the amount it can move.
(If you wanted to make it worse, the player must move that exact distance.)
Thus the player is at the mercy of a completely unpredictable dice, and can move anywhere from 1-20" per turn.  There is no way of making any plans, because you don't know with any degree of certainty what you or your opponent can do.

Predictable Random
Okay, let's replace that d20 with d6s.   4d6s would result in a move between 4-24" - the same 20 point spread. But due to the bell curve of the multiple dice, you can rely on a move of ~14".  Probably around 10-18" most times.   It's still unpredictable, but you at least have a guesstimate of what you can do, thus allowing him to plan ahead and formulate tactics instead of only reacting to dice results.   If you allowed the player to choose any distance up to the total, it would make it even more reliable. 

UNSEXY MODIFIERS
These have become a bit unfashionable of late. I think this is a reaction to some 90s rules, where there was a modifier for everything.
-1  captain ate baked beans this morning
+1 great Sports Illustrated issue this month
-2  hungover
-1 out of coffee
-1 undergarments too itchy
I agree they can be a problem. Too many modifiers are confusing, and negative modifiers are annoying (I mean, it annoys me if I roll a '6'  and I don't get a hit cos of that -3 modifier.  Buckets of Dice is a common trend (probably worth a post of its own) and it too has modifiers - only you simply add/remove dice rather than modifying the score of the dice.

However modifiers are important for determining tactics.  Infinity does a great job of this.  Let's say a soldier needs to roll a 10+ on a d20 to hit, and a 10+ on a d20 to wound.  Being in cover adds +3 to both rolls, which gives a strong incentive to stay in cover while not making it impossible to hit troops in cover.  Modifiers are important.  They help steer your players to play the game the way you want them - whether historically or otherwise.