…it’s about consequences of failure.
In most RPGs, when a player declares an action, you as the GM declare how hard or easy the task is. This usually takes the form of a penalty or bonus. Seems easy enough, right? Remove or add an extra dice to the pool, subtract or add a bonus +/- 10 or +/- 1. Easy.
HOWEVER, it gets weird when there are multiple modifiers. for example, take this all-too familiar situation.
Player: “I attack the goblin!”
GM: “Cool, you have the higher ground. THat’s +1. AND you outnumber him, so that’s another +1.”
GM: “Wait. You have a sprained ankle. That’s -1. And it’s raining. THat’s another -1.”
Player: “But remember, the cleric blessed me earlier. That’s another +1”
GM: “True. Okay roll the dice– oops wait a second, there’s another -1 because you’re still hung over from last night’s drinking binge. What’s the total bonus or penalty now?”
Player: “uhh… 1 + 1… that’s 2… minus another 2… that’s… nothing. But +1… and -1… Nothing. Uh… okay what a waste of time. I just roll regularly.”
* rolls the dice *
GM: “You miss. Okay, next player…”
AAAARRGHHHHH that sort of crap makes me hate RPGs.
My recommendation? DITCH MODIFIERS ALLTOGETHER. Or, at the very least, limit them to a single max bonus. Ditch penalties in that case.
But how do you imply the difficulty or challenge? Make the consequences of failure WORSE. You see, with all those modifiers, you still have to come up with a failure situation ANYWAY. So why bother at all?
Limit modifiers. Instead, focus on what happens IF they fail. Much easier and interesting for everyone, I promise.