Each incursion is three obstacles, back to back. For each one, commit an Approach — one of your operative's four stats: Offense, Intuition, Defense, or Intel. Every obstacle favors one approach and resists another: lean into the favored one and it's easier, walk in with the resisted one and it's harder.
Your effective strength for that roll is your chosen stat, scaled by momentum — consecutive successes build it up, a failure resets it back to baseline. A d20 is rolled against the gap between your effective strength and the obstacle's difficulty rating: the wider that gap, the more lopsided the odds swing toward whoever's stronger. But a natural 20 always flips the result regardless of who's favored — there's no such thing as a guaranteed pass, and no such thing as a guaranteed loss.
Clear all three obstacles and the incursion is a flawless success. Fall short and the outcome scales down from there — even a rough day still completes the incursion, just for less.