[Slipperychicken]

Street Grimoire 172-173 gives rules for the Motion Sense power, but I am left with some questions even after cross-referencing the core book's segment on detection magic.

-How should I determine the level of detail given about each moving object? I'm thinking of using either the "Detection Spell Results" table (core 286) or "Perception Thresholds" (core 136) to decide how many net hits are needed to notice a given detail.

-Is the power always-on? I noticed Street Grimoire did away with the active/passive distinction. If an adept with the spell active is strolling through a cube farm, would he make his perception+magic[mental] roll to sense all of the wageslaves' motions (typing, breathing, sipping their fifth cup of soykaf, tapping at commlinks under their desks, etc) as if the adept was using his eyes and ears? Or would he need to make a special effort or spend an action to notice?

-How do you guys have the power interact with the environment? Would you let an adept with this power notice water flowing through pipes inside walls, the spinning of a fan, the opening or closing of a door?

[Officerzan]

Let's start by the fact that it isn't detection magic and you shouldn't cross reference anything. Powers don't follow spell rules and spells don't follow power rules.

That said, moving on. Depending on your GM, it is either a Halo/Call of Duty style minimap where everything you sense is a blip, or it's literally just that you know something moves in the area. Either way, there are no details to give. The adept may know someone is moving through the "empty" room he is in, however, he doesn't know that it is a big ass troll named Bear with a combat axe (via the Motion Sense power that is).

It's kind of both. I secretly roll it if it should come into play (a drone spying on them) or I let the player roll if the they decide to observe their surroundings in detail (leaning against the corner to sense if someone is patrolling. If you roll for every dripping pipe, rat, and twitchy keysmasher, it just becomes tedious.

[Tecumseh]

I have an adept with the power. The interpretation can be tricky, as you've found.

First off, there's the relative nature of motion. If the adept is standing still near a parked car, then there's no motion to detect. But if the adept starts walking, can they then sense the car because the car is moving relative to the adept? Based on the fluff, I'm inclined to say yes, but with the caveat that this isn't the Spatial Sense spell. You can't completely map your surroundings simply because you walked by, but it will give you a shot to "feel" some of the nearby features, like the invisible troll waiting for you with a combat axe.

I usually call it out and roll when I specifically want to use the power, but I trust my GM to alert me (or roll on my behalf) when there's an obvious situation where the power applies, like Bear the troll sneaking up on me.

As a GM, I would allow for more details than Officerzan describes. You might not be able to distinguish between a troll named Bear and an actual bear, but you could probably figure out that it was a mammal vs. a drone or a vehicle. Per the table on p. 173, the approximate size would be an appropriate piece of information to share. I wouldn't let the power sense micro-movements like typing or soykaf sipping, but the adept could probably distinguish between macro-movements like walking or skipping rope or commando crawling. I try to err in the adept's favor, remembering that this is something that the adept has had most of their life, and thus they have some experience in interpreting.

The environmental questions are interesting. I would say yes to all the examples listed. Again, details will be minimal - they don't know if it's water in the pipes or delicious hurlg - but they could reasonably determine that something is moving. The paid half a power point for it, so I think it should tell the player something rather than providing a simple yes/no to the question, "Is something moving?"