Harsh Light of Day
Here is the basic run-down of how tests will work in Harsh Light. Essentially, this boils down to converting the mechanics found in Vampire: The Requiem and World of Darkness to a single card-pull system, which isn't terribly complicated.
The core concept works the same as most World of Darkness games – a pool of Attribute + Skill, against either a set difficulty or another character's pool. The most important difference is that instead of rolling multiple dice to determine successes, you pull a single card value from 1-10 and add your pool to that number.
Similar to tabletop WoD, how well your character does is measured in successes, with most tasks only requiring a single success to accomplish, but some requiring more. When you pull a card and add your pool, you get your first success at a total of eight (for example, a pull of three + a pool of five), and every three points above eight is another success. The totals required for one to five successes are as follows:
8: 1 success.
11: 2 successes.
14: 3 successes.
17: 4 successes.
20: 5 successes.
There are a couple of cases where things work a little differently. A pull of 10 (or, with certain powers and/or equipment, even 8 or 9) allows you pull a second card, adding both cards to your pool for your total. Pulling a second 10 in a row doesn't let you keep adding, but you're adding +20 to your pool now, so enjoy that!
The other exception is when your Attribute + Skill pool has been reduced to 0 or less due to difficulty or penalties. In this case, you may still attempt the action, and hope that luck carries you through, but there is a risk: If you pull a 1 while using a pool of 0 or less, you have Dramatically Failed! Dramatic Failure is worse than simply not succeeding, it means something particularly nasty has happened: your weapon breaks, you injure yourself, horrifically insult the person you're talking to, etc. Most Disciplines have their own specific rules for Dramatic Failures, but at any other time what happens to you is up to the discretion of the Storyteller or Narrator observing the test.
This system does mean that you can achieve automatic success: If something only takes a single success to achieve, and your pool is 7 or above, then you will accomplish the task automatically, without needing to pull a card (assuming no penalties, of course). This continues on if you need two successes and your pool is 10, etc. etc. Note that you can still pull a card if you want, as some tasks give greater results based on more successes achieved.
Finally, if you get a total of 5 or more successes (20+ on your test) you have achieved an Exceptional Success, which may grant additional effects (especially when activating supernatural powers). Much like Dramatic Failure, unless specific rules are in play, what happens in the case of an Exceptional Success is up to the Storyteller or Narrator, but it will always be beneficial!
Instant: An Instant Action takes little time, but still requires focus. In combat, you get one instant action per turn (attacking, activating most powers, etc).
Reflexive: Similar to a Free Action from D&D, you can take several Reflexive actions per turn (within reason). Examples include talking, activating simple powers, or resisting an opponent's power.
All characters may move their Speed in steps as a reflexive action once per turn (unless somehow restrained).
Simple: The one keyword not in the book, a simple action is one where you just pull a card, either making enough successes or not. Most tests fall under this category.
Extended: These are actions that take a variable amount of time to complete – picking a lock, building a car, or trying to find that one bit of information in a library. The player pulls cards until they have accumulated however many successes are needed (perhaps five to pick a simple lock – up to 25 to build something large and/or complicated), with each test taking up an appropriate amount of time (examples: a combat round for lockpicking, an hour for research, or a day for large-scale construction).
Resisted: Resisted rolls are where you subtract an opponent's pool from your roll – generally either Defence or a Resistance trait (Resolve, Stamina, or Composure). Nearly all attack rolls will be resisted by Defence.
Contested: A contested action is one where you are directly competing against another character (running a race, solving a puzzle, or scoring points in a contest). Both pull a card, add their pools and compare successes, with the higher number of successes winning. Vampires will often add their Blood Potency to their Resistance traits when rolling vs. supernatural effects.
Some tests are both contested and extended – in those cases, you continue pulling until one of the characters reaches the required number of successes.
Useful things to know:
There are very few retest powers in NWoD.
Spending a point of Willpower adds 3 to your pool for a pull (generally adding a success) or adds 2 against a Resisted test (including attacks – spending a Willpower for +2 Defence can be a lifesaver in emergencies).
You may only spend one Willpower per turn (including Willpower spent to activate powers).
Each attack on an enemy lowers their Defence by 1 until their next action – gang up on people, try to avoid being ganged up on.
You can give up your Defence for a +2 to your pool in melee (known as an All-Out Attack), or give up your attack to double your Defence until your next turn (known as a Dodge move).
Defence usually doesn't apply against most ranged attacks (unless your attacker is within arm's reach). The notable exception is Thrown Attacks, which do take Defence into account due to the relatively slow speed that the missile is traveling.