New Gathox Mechanic: "Clear20"

 Howdy folks!

In my endless quest to make combat faster and less mathy, I've brainstormed a simple mechanic for attacking and saving that I believes alleviates two problems:

1) The absurd and seemingly endless statistical inflation of ascending armor class; and
2) The confusing and tiresome math of To-Hit scores combined with subtractive armor.

That mechanic is called "Clear20."

A Clear20 roll happens (surprise!) on a 1d20, where the player needs to roll a 20 or higher. It's used for combat and saves, as follows:

Attack Rolls
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Once intitiative has been determined, PCs and NPCs may attack on their respective initiatives. Defense is passive; no one rolls for Defense. Combatants only roll to Attack, and this is achieved with the "Clear20" die mechanic.

Clear20: roll 1d20 and add the appropriate modifiers. If the resulting number equals or exceeds 20, the roll is a success.

In the case of attacking, a combatant adds the following:

1. Base Attack number. All L1 PCs begin play with at least 1.
2. The opponent's Defense value. This ranges from 9 at worst to 0 at best.
3. Situational modifiers.
4. Environmental modifiers (optional).

Situational modifiers include:
* All PCs add or subtract their DEX modifier to ranged attacks.
* Militants add or subtract their STR modifier to melee attacks.
* Mentalists add or subtract their INT modifier to physical attacks with magic weapons.
* Mutants add or subtract their CON modifier to physical attacks with bodily mutations.

Environmental modifiers include:
* -1 for fighting in fog, noxious clouds, rain, snow, loose debris (sand/rubble), starlight, or fighting from low ground.
* -2 for fighting in sandstorms, monsoons, confined quarters (less than 10' wide), mud, viscera, or while surprised.
* -3 for fighting in water/liquids, low/zero gravity, darkness, blinding light, the psychosphere, or while bound, flying, or falling.
* -4 for fighting after reduced to 0 HP and rolling for Death and Dismemberment (assuming the PC lives and can somehow fight).

The Slumlord may adjudicate additional situational or environmental modifiers as they see fit. The severity of additional modifiers ought to be in accordance with those listed above.

Saving Rolls
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A Saving Roll is required when a PC is subject to a life threatening situation or condition. This may include falling, poison, shock, magic, being reduced to 0 or fewer HP, or deadly traps. Unless mandated by an effect, the Slumlord judges the necessity of a Saving Roll on a case by case basis. These rolls ought to be infrequent, and are also governed by the "Clear20" rule:

Roll 1d20 and add the appropriate modifiers. If the resulting number equals or exceeds 20, the roll is a success.

PCs making a Saving Roll add the following:

1. Their base Save score. All L1 PCs begin with a base Save of 4.
2. Their level.
3. Explicit modifiers from  gear, magical or technologically advanced items, magic, and psychic abilities.

The Slumlord may assign additional modifiers as deemed appropriate. Keep in mind that successful Saving Rolls may:
* negate a situation
* halve an effect
* forestall a condition
* avoid death
* create room for a less harmful outcome
* halt a perpetual or active condition which otherwise cannot be halted

Saving Rolls should not apply to:
* social interactions or roleplaying interactions
* negotiations or bartering
* melee or ranged combat damage
* carousing, downtime activities, or spending RP
* situations in which lethality is not of immediate, paramount concern

Let me know what you think in the comments!