The core mechanic for the Lighthouse System is simple. Roll a d20 and add modifiers. If the roll is high, 11 or greater, you succeed. If the roll is low, 10 or less, you fail. There are no variable difficulty numbers, no charts, no tables. High or low. Everything else is accounted for in the modifiers, assigned by the guide, and those are bog-simple as well. I’ll explain those in another post.
You also need to pay attention to whether the result was even or odd. If it’s odd, the gamemaster narrates the outcome. This is the standard situation in most roleplaying games. Whether you succeed or fail, they describe what happens. In Lighthouse, an even result means that you describe the outcome. Make your successes look awesome. Have your failures seem less painful.
The shared narration has had some interesting results in playtest. What it’s ended up doing in my group is fostering greater cooperation. You don’t want to get too arrogant about describing your own successes, because that can come back to bite you the next time the guide narrates. The descriptions end up being cool, but generous toward the involvement of other characters.
Descriptions of failure, interestingly enough, don’t always come down to excuses. They can be, but it’s been fascinating watching players own the characters’ mistakes. They tie it in to recent events, things on their characters’ minds, and plain bad tactics. It gives them something to roleplay off of in the next turn, and throughout the scene.
This mechanic provides the random element that makes tabletop roleplaying fun, without getting in the way. It’s there when you need it, but you don’t need to bring things to a grinding halt. Pause, roll, interpret. My players have tended to stay in character longer, making the experience more immersive. They react to “bad” rolls, whether that means failure or not being able to narrate, in ways that show me that they’re invested in the whole story, not just their characters.