Attributes

A Few Notes...

First; in Ground Zero they're called 'attributes' not 'ability scores'. I just like that name better.

Second; attributes are rolled 'old school' style; 3d6 for each, in order. Players can adjust their PC's scores by spending Build Points, but you might have to change your character concept based on the initial rolls. The point buy system is not the same as the planned generation methods in d20 Modern or D&D - see below for details.

Third; because of the way hit points are handled in Ground Zero, Constitution may appear somewhat useless. Don't be fooled - your Con score is also vital with respect to massive damage threshold, Creep threshold, and saves vs. environmental hazards.

Attributes:

Every character in Ground Zero has six basic characteristics, called 'attributes'. The six attributes are Strength (abbreviated Str), Constitution (Con), Dexterity (Dex), Intelligence (Int), Wisdom (Wis), and Charisma (Cha). All of these work exactly the same as in standard d20 games, except for Constitution.

In Ground Zero, attributes are randomly determined. You can use Build Points to raise (or lower) your attributes as you like, but race, background, mutations, experience, and exposure to hazardous agents can all modify these scores in the end.

Determining Attributes:

Attributes are determined randomly. Roll 3d6 six times, in order, to obtain Str, Con, Dex, Int, Wis, and Cha. Chances are you'll get a couple decent rolls, plus one or two that suck. You have a number of Build Points (20 or 30 in the current campaigns) that you can spend to bring up your low attributes, but it may not be worthwhile to raise your Dex from 4 to 16, for example. Hope you weren't planning on playing a sharpshooter.

Do not add attribute modifiers for genotype, background, or mutations yet - they are applied at the end of the character creation process. Note that you can wait until after you roll mutations before spending BPs - you'll probably want to know your mutations before adjusting attributes anyways.

Changing Attributes:

All characters can spend Build Points to improve their attributes, as shown below. You can also choose to have decrease one or more attributes to gain extra BPs. Higher attribute bonuses cost comparatively more BPs than lower attribute bonuses, but large penalties do not accrue many extra BPs. Build Points can also be spent on mutations or to pick up Karma Points; they do not all have to spent on attributes.

Raising Attributes

Attribute Raise (BP Cost)
3 to 4	1 BP
4 to 5	1 BP
5 to 6	1 BP
6 to 7	1 BP
7 to 8	1 BP
8 to 9	2 BP
9 to 10	2 BP
10 to 11	2 BP
11 to 12	2 BP
12 to 13	2 BP
13 to 14	3 BP
14 to 15	3 BP
15 to 16	4 BP
16 to 17	4 BP
17 to 18	5 BP
18 to 19	5 BP

Lowering Attributes

Attribute Drop (Bonus BP)
3 to 2	1 BP
4 to 3	1 BP
5 to 4	1 BP
6 to 5	1 BP
7 to 6	1 BP
8 to 7	1 BP
9 to 8	1 BP
10 to 9	1 BP
11 to 10	1 BP
12 to 11	1 BP
13 to 12	1 BP
14 to 13	1 BP
15 to 14	1 BP
16 to 15	1 BP
17 to 16	1 BP
18 to 17	1 BP

Remember - characters add modifiers for genotype, background, and mutations after spending BPs. This can bump some scores higher than could normally be afforded, while making it very costly to have extremely good scores in other attributes.

Constitutuion in Ground Zero:

A character's Constitution modifier is applied to:

Fortitude Saves: Add your Con modifier to any Fortitude saving throws for resisting disease, poison, and radiation; enduring critical effects; and similar threats.
Endurance Checks: Constitution is the key attribute for the Endurance skill, which includes any long-term physical activity (long-distance running, staying awake, and drinking contests) as well as anything covered by the Concentration skill in a standard d20 game.
Disabling Injury: Under the regular d20 rules, a character reduced to less than 0 hit points is automatically unconscious. In Ground Zero, a character with a Constitution bonus may continue to act as if disabled until his negative hit point total exceeds his Con modifier.

Your Constitution score also determines base hit points, massive damage threshold, and Creep threshold. Small-sized characters receive a -2 penalty to these values, medium-sized characters have no modifier, and large-sized characters receive a +4 bonus:

Base hit points (hp): This is the number you start with before any hp for class levels, mutations, etc. are taken into account.
Massive Damage Threshold (MaD): You are required to make a Fort save to avoid being disabled (brought immediately down to 0 hp) whenever any single attack inflicts more damage than the character's MaD threshold. The save DC is 15 + 1 per every 5 points of damage. The amount of damage a severely injured (negative hp) character can suffer before dying is also equal to his MaD threshold.
Creep Threshold: As the character is exposed to diseases, poisons, and radiation, he suffers effects from the Creep. A character's Creep threshold represents his body's tolerance to cumulative Creep exposure. See the Creep page for details.

Finally, a character's percentage chance to stabilize each when unconscious or dying is equal to his Constitution score (without the size modifier).

The extra hp from a high Constitution make a difference at lower levels, but are less important for high-level characters. Conversely, the massive damage threshold is rarely an issue at low levels, but can be a matter of life or death for more experienced characters.

Note that Constitution does not modify hit points gained for class levels. High-level PCs in Ground Zero will not end up with as many hp as characters in other d20 RPGs.