Sphere RPG Mecha Resolution System

Mecha and other war machines are unsurprisingly a core part of Sphere and have their own statlines, and for the following section 'Mecha' can be taken to read as any vehicle-sized object such as tanks, airplanes, giant robots, etc. Starships and similarly-sized entities are broadly similar with a few additional rules to reflect their size.

Key Concepts

Combat Flow

This is recopied here to show the differences of vehicle combat.

Initiative Step (rolled at start of combat or when an entity attempts to Take Initiative)
1) Roll initiative (physique + wits) vs 6

Proceed in order of success

Tactics roll can be used to give additional auto-sux on initiative roll to all friendlies.

Action Steps (cycles through entity by entity)
2) Recover AP (Action Points)

All vehicles recover AP.

Additional AP may be gained by some actions (jump out of ambush, etc)

Compound vehicles (eg, ships) do not recover AP; their large crew complements and integrated command systems means they have modified action effects. See below.

3) Compound Vehicles take mobility type actions that affect further rolls. Eg flank speed, evasive, etc.
4) EWarring. This allows for an attacker to bypass a defender's PP. Really intended only for Compound vehicles.
5) Take action by spending AP (example below: shooting!) Note that vehicular combat is a bit more complicated than character-level combat due to the wider spread of weapons and defenses.

Shooting is done with the standard Stat x skill pool, with further modifiers derived from situational modifiers.

• 'Guns' use Gunnery x Perception and defended against with Piloting
• 'Missiles' use Electronic Warfare x Intellect and is defended against with Electronic Warfare
• 'Cannons' use Artillery x Intellect and defended against with Piloting or Electronic Warfare
• Melee weapons use Mecha Melee x Wits and defended against with Mecha Melee
  • In space combat, Agility is added on both the attacker's and defender's side.
  • Craft Stealth can substitute for Electronic Warfare on the defense.

On the ground, cover provides passive evasion and increases difficulty.

Burst adds dice as per normal

Protection Steps
6) All attacks that hit ablate 1 or more PP (Protection Point). An entity with 0 PP before the attack goes to Damage Steps instead.

‡‡

Damage Steps
7) Determine Damage Target

Damage target is (target's [Armor + Screens] - weapon's Penetration); this may not go below 3.

Some light (or sub-scale) weapons may have a negative penetration modifier. This will increase the effective armor value.

Weapons with the Piercing X tag add X to their Penetration; Screens reduce this by up to the Screen rating.

Weapons with Precise get a +1 Power modifer for every excess success that they score on the to-hit roll.

8) Roll damage

Roll weapon's Power dice against the Damage Target. Add up number of successes and compare them to the target's damage threshholds.

For Standard Vehicles these are Damaged/Destroyed.

For Compound Vehicles these are Surface Damage/Internal Damage/Critical Damage

Damage tables? Flat dice penalties are unrealistic on this level. A more Silhoutte-styled simple damage roll would fit.

‡ Test idea: *Effective* Agility is capped at Physique - dealing with instantaneous G-forces etc.

‡‡ Test idea: Every sux on the to-hit roll ablates one PP.

Potential idea: Allow for shooting 'through' PP at a penalty of +1 difficulty per points of PP. A success attack acts as if the target had 0 PP, a failure/miss does not ablate any PP. This allows for the introduction of 'one shot kills' without drastically altering the general gameflow.

Additional optional rule: If more 10s are rolled on the to-hit roll than the target has PP, it hits as per above. No PP is ablated.

AP actions include:

Shooting/Fighting

Moving

Recovering PP by finding new cover or better positioning - being tacticool

Misc actions Doing Things

Compound Vehicles:

Compound Vehicles have large crews and integrated command systems, allowing them to do many things at once. As such they can fire all their valid weapons, perform all valid Electronic Combat actions as well as any other miscellaneous actions. As well, any maneuver action they take affects all subsection actions that turn, for good or ill.

Most Compound Vehicles are unable to make Piloting or Mecha Melee passive defenses, though they can make Helmsman passive defenses against Super-class weapons.

Thing to do: Determine best way to compensate for fighters. Simply have high accuracy for turrets? Probably.

Tags

Tags are various features that weapons can have, each giving special effects above and beyond the base statline. Following is a list of all Tags and their effects.

Limited Ammunition X is for weapons with small ammunition loads. The X is how many shots the weapon has before it must be reloaded.

Missile is a tag for weapons that use large, self-guided projectiles with onboard propulsion. Missiles may be defended against (shot down) by Point Defense. Many missiles also have Smart (see below).

Smart X is for weapons with onboard guidance and re-attack capability. As such if they fail to strike or ablates a target's PP, they may roll again ('re-attacking'), continuing on up until they strike or run out of Smart re-attacks.

Piercing X is for weapons that have advanced armor-piercing designs, giving them a bonus against hard argets. For every level of Piercing the weapon's effective Penetration is increased by one. Unfortunately these weapons tend to by stymied by forcefield-based defenses and consequently Screens reduce the Piercing bonus on a 1-to-1 ratio, to a minimum of 0.

Disruptor X is for weapons that have enhanced ability to penetrate defensive forcefields. For every point of Disruptor, the target's Screen bonus is reduced by 1, to a minimum of 0.

Assault X is for weapons that have an extremely high rate of fire and can easily put a large number of beams or shells on a target in a short period of time. For every Xsuccesses above that required to hit, the weapon scores an additional hit with a threshold of 0, resolved as per normal rules.

Parry X is for weapons that have the ability to block or deflect other weapon attacks, generally melee. Specific TBD

Un-Updated Stuff

Mecha Stats

The following stats are the core values for mecha and serve to describe the platform itself.

Agility: Agility is a measure of how responsive a mecha is to its controls. Agility adds a positive modifier to to-hit rolls made against the mecha, as pilots will naturally take advantage of a machine's agility to avoid shots. Agility also adds a negative modifier for melee attacks' to-hit rolls.

Speed: Speed is a measure of how fast a mecha moves. Speed can also be used to Zoom and Boom (see Advanced Actions below).

Strength: Strength is a measure of how strong a mecha is. It acts as a negative modifier for melee damage and additionally is the size limit for any non-fixed weapons - weak mecha can't exactly carry around 500mm hyper mega autorails.

Output: How much Power the mecha's onboard power system generates per turn. This may be 0 for vehicles or mecha with fixed-output power systems or battery-powered units.

Battery: The maximum amount of Power a mecha's onboard power system can store. The amount of Power in a battery may temporarily exceed its maximum value - the hyper mega beam cannon is being powered directly by the reactor while also drawing down the battery. Any excess at the end of the turn is removed.

Electronics: This is a measure of the generalized onboard electronic gear of a mecha, ranging from sensors to targeting equipment to ECM. See the Special Moves section for the full effects of Electronics.

Stealth: This is a measure of how difficult a vehicle is to detect with sensors. See Advanced Actions for more detail.

Armor: Armor is a measure of how difficult is it to breach the physical defenses of a mecha. Armor is the target number for Penetration rolls.

Resilience: Resilience is a measure of how resistance a mecha is to damage. Resilience subtracts from the damage inflicted by weapons strikes.

Durability: Durability is essentially how difficult it is to render a machine unable to fight. More durable mecha can fight longer. It is essentially the mecha's 'hit points'.

Carrying: This is a value for how much 'stuff' a mecha can carry externally, such as mecha-scale assault rifles, missile packs, sensor pods, etc etc. Most giant robots and aircraft have high carrying values as they use externally-fitted weapons. Carried weapons and systems provide flexibility, but the downside is that they are much easier to lose.

Weapon Stats

Weapons have their own distinct statline with several values as follows.

Accuracy: Accuracy is a measure of how easy it is to hit with a weapon, and it adds a negative modifier to to-hit rolls.

Burst: Burst is a measure of how fast a weapon can fire and adds its value to the dice pool on to-hit rolls.

Slow: This is for weapons with extremely long cooldown periods; a weapon with Slow must wait for that many rounds to fire again.

Range: This is how far the weapon can fire accurately. Going up to double this imposes a -2 Accuracy modifier, tripling -4, so on.

Penetration: Penetration is the dice pool rolled to penetrate Armor on a successful hit.

Strength: Strength is how much additional Durability damage a weapon can inflict and can also be used to reroll Penetration dice. Generally speaking, Strength correlates to explosive power/area of effect; Strength 0 is pure kinetic/energy impact and increasing levels represent some form of explosive effect.

Draw: How much Power a given system needs per turn simply to remain active. Systems can be activated or deactivated as desired, though they can only be on or off during a specific turn.

Charge: How much Power a given action takes; for example a flash Field might have a Draw of 1 for standby and then have a Charge of 1 per attack blocked.

Weapon Abilities

Hardened: The weapon is strengthened with integral forcefields and energy-dissipating alloys. It can be used to parry/block Overpower weapons without being destroyed.

Disruptor #: The weapon has enhanced ability to penetrate non-physical defenses. It reduces the Field rating of a target by the Disruptor rating.

Armor Piercing #: The weapon has enhanced ability to penetrate physical defenses. The difficulty on Penetration rolls is reduced by the Armor Piercing rating.

First Strike: The weapon can strike from beyond normal melee range and consequently gets an extra attack upon entering melee combat.

Entangling: Can be used to disable an enemy's weapon (normally melee). Specifics TBD

Grapple: If an enemy fails the first roll (Seek Opening) in a Melee Lock situation, the Grappler may immediately make a counterattack as per normal rules.

Overpower: The weapon will automatically destroy any non-Hardened, non-Overpower item used to block it. Crunch!

Limited Ammunition #: How many shots the weapon has before it needs to reload (available seperately). This typically represents weapons that have bulky, heavy ammunition.

Precise #: The weapon is optimized for high-precision attacks, including enhanced targeting equipment, accurized barrel, etc. For every # successes above those required to strike, the weapon gains +1 Penetration.

Scatter #: The weapon has a variable-aperture muzzle, adaptive focus or some similar feature that lets it 'spread' its shot widely at the cost of terminal effectiveness. For every point of Penetration spent, the weapon gains +# Burst.

Assault #: The weapon has an extremely high rate of fire and can easily put a large number of beams or shells on a target in a short period of time. For every # successes above that required to hit, the weapon scores an additional hit, resolved as per normal rules.

Advanced Actions

The rules above cover basic combat as portrayed in most scifi, with intense close-range furballs and madly jinking attack craft. While these will suffice for games that do not have a strong vehicular combat component, for ones centered around military units or other situations where giant robot combat is common the following rules provide greater depth and diversity.

Melee Lock

Mecha fighting each other with melee weapons can be likened to humans doing the same. And like their small counterparts, a mecha trying to disengage from a melee fight risks getting hit before it can open the intervening distance. This is Melee Lock, the tendency of melee combatants to stay in melee.

Breaking Melee Lock is an action, with associated penalties if multiple actions are taken. It is an opposed roll, Mecha Fighting modified by Agility. If this roll is failed, there is no effect; an opening is not found. If it is successful, the initiator must now roll Piloting/Speed against the enemy's Mecha Fighting/Agility. If this second roll succeeds, the initiator can immediately make a normal move. If the roll is failed, the enemy can immediately make a counterattack at current penalty (if any), and then the initiator can immediately make a normal move.

If any time a melee combatant botches a melee weapon strike roll, the enemy craft can disengage from Melee Lock with no roll and move its remaining move away, if desired.

Zoom and Boom (aka Lightning Strikes)

While the normal flow of combat assumes that fightercraft will be engaged in turning contests and complex, high-agility maneuvers to gain position, in some situations high-velocity craft will instead perform rapid strikes before pulling away to come about for another pass. This is common in air combat and rather less so in vaccum.

In space, a Lightning Strike allows the performing unit to accumulate excess velocity above the norm and essentially 'slash' past the target(s), firing all weapons then (hopefully) coming about outside of the target's defensive envelope. For every turn a unit is Lightning Striking, it may increase or decrease its maximum move by 100% (one 'level'); however, its minimum move is also increases (or decreases) by one full level. EG, a mobile suit with move 5 doing a lightning strike can move between 6 and 10 spaces on its first turn. Machines doing Lightning Strikes must also move their minimum distance before making a turn of no more than one side.

A craft doing a Lightning Strike has other advantages; it replaces its Agility with its Speed for offensive

Dive Bombing (aka landing on a spaceship and shooting the crap out of it, point-blank)

Mecha that are at 0 or 1 range from a ship are assumed to be 'dive bombing', which allows them to ignore many defenses a ship has as well as precisely place their shots in weak spots.

Stealth

Hiding