This section contains brief explanations of key rules. It's not the entire rulebook, for two reasons: firstly that I don't want to write an entire rulebook, and secondly that even if I did there might be parts I wouldn't show to the players.
These rules may eventually be firmed up a little and used for other games, besides the Screaming Twenties. For that reason they're a little more general in scope than I expect to be necessary in that game. If you're playing in that, don't expect masses of firearms combat just because I happen to include a few pieces on it.
So, we're on an Interlock (CP2020) variant: variable target numbers for skill rolls of:
Attribute + Skill + Bonuses + d10
The Attributes we're going to use are the following:
I know, they're not the normal Interlock stats. I've split the functions of Reflexes down into Reflexes and Coordination so that a single trait isn't so key to combat characters. I've taken Move Allowance away because I don't think there should be such a broad range of movement speeds along humans (Run is likely to be calculated as 10 + Reflexes + Body rather than 3*MA). I've replaced Attractiveness with Charisma, because I wanted to make it slightly more generic than what has traditionally been considered by players to be little more than sex appeal. Cool/Will is now called Willpower, shortened to Will, because somehow using the word 'Cool' to describe the beautiful people of 2020 seems trivial or worse.
Luck remains. Although the exact mechanics of using it aren't yet settled, Luck will not be a dump stat; people who have it unreasonably low may find themselves in trouble.
Normal human range for these is 2-10.
A skill list will be produced later. Skills won't be specifically related to particular attributes, but there will generally be one or two common combinations, much as in the Storyteller system.
Skills run from 0 (unskilled) to 10. The referee will be left to decide which rolls can be attempted unskilled, or whether alternate skills may be used instead.
The main category of bonuses is from a set of nWoD-style Advantages. These run from 1-10, and may offer different bonuses at different levels. For example, the new Combat Sense adds a cumulative +1 to awareness rolls in combat situations at each odd level, and +1 to initiative at each even level.
Other bonuses added into skill rolls will generally include equipment bonuses, or others that the player is responsible for keeping track of. Circumstantial modifiers will generally be applied to the target number instead.
When the d10 comes up 10, roll again and add results. If necessary, keep rolling and adding until something other than 10 is rolled.
If the initial d10 (not extra d10s for rolling 10s) comes up 1, roll another die and take it away. Inform the ref if this penalty die equals or exceeds your Luck.