Generation I lab
Special stat and critical hits in Pokemon Yellow
Yellow still uses pure Gen I rules: one Special stat for both sides of special damage, crits driven by base Speed, high-crit moves like Slash, and the infamous Focus Energy glitch. Use the live calculator to see real percentages.
Fast Answer
Speed for crits, Special for both ends
When Alakazam attacks with Psychic, its Special powers the hit and the foe’s Special defends—same number, both roles. Critical chance ignores X Speed and paralysis; it reads the species base Speed. High-crit moves (Slash, Razor Leaf, Crabhammer, Karate Chop) jump that rate. Focus Energy does the opposite of what it claims.
Pre-split Special
One Special stat explained
What Special does
- Powers special-category damage (by type, not by move “category” text in later games)
- Defends against special-category damage
- Has its own DV and Stat Exp pool
- Splits into Sp. Atk / Sp. Def only starting in Gold/Silver
Physical vs special by type
In Yellow, the attacking type decides which stats are used—not the move’s later “physical/special” label.
Physical types (use Attack / Defense)
Special types (use Special / Special)
Fire Punch is “special”
Even though it is a punch, Fire is a special type in Gen I, so it uses Special—not Attack.
Body Slam stays physical
Normal is physical, so Attack and Defense apply even on bulky special walls.
Yellow type quirks
Ghost fails into Psychic; Bug is super effective against Poison. Full interactive chart: Yellow type chart.
Critical hits
Yellow critical hit formula
The engine builds a threshold from base Speed ÷ 2, then scales it for Focus Energy and high-crit moves. A random roll is compared to that threshold (capped at 255). Rough player-facing rates:
| Situation | Threshold (before cap) | Approx. chance |
|---|---|---|
| Normal move, no Focus Energy | Base Speed ÷ 2 | (Base Speed / 2) / 256 |
| High-crit move, no Focus Energy | Base Speed × 4 | min(255, Base Speed × 4) / 256 |
| Normal move + Focus Energy (bug) | Base Speed ÷ 8 | (Base Speed / 8) / 256 |
| High-crit + Focus Energy (bug) | Base Speed | Base Speed / 256 |
High-critical moves in Yellow
| Move | Type | Power | Acc |
|---|
Focus Energy glitch
Focus Energy sets “Getting Pumped,” but the crit routine shifts the wrong direction. You get about 1/4 the normal crit rate, not a boost. Do not open with Focus Energy if you want more crits.
- Dirge for Slash teams that “set up” Focus Energy
- Still wastes a turn on most mons
- Fixed in later generations
Why Slash “always” crits
Persian’s base Speed is 115. High-crit threshold ≈ 115×4 = 460 → capped at 255 → 255/256 crit rate. It is not literally 100%, but it feels that way.
Crit damage
A critical hit doubles the level factor in Gen I damage (and ignores negative stat stages on your offense / positive stages on their defense in the classic reading). Use the damage calculator for exact rolls.
X Speed does not help crits
Only the species base Speed in the header matters for the rate test—not the in-battle Speed stat after modifiers.
Interactive
Critical hit chance calculator
Formula mirrors Yellow’s critical-hit test: start from base Speed/2, apply Focus Energy and high-crit scaling, cap at 255, compare to a random byte path equivalent to threshold/256 for planning.
Progression stats
Badge boosts, DVs, and Stat Exp
| Badge | Stat boosted | Rough effect |
|---|---|---|
| Boulder | Attack | +12.5% (×1.125) when applied |
| Thunder | Defense | +12.5% |
| Soul | Speed | +12.5% |
| Volcano | Special | +12.5% |
Full obedience ladder, dialogue-vs-code notes, and a restack calculator: Badge boosts tool.
DVs (hidden “IVs”)
Each mon has Attack, Defense, Speed, and Special DVs from 0–15. HP is derived from the other four. Trainers often use fixed DV sets in data; wild mons vary. Use the site calculators to reverse stats.
Stat Exp ≠ modern EVs
Beating Pokémon still raises hidden Stat Experience toward each stat (and HP). The cap is 65535 Stat Exp per stat—not the Gen 3+ 252 EV system. Vitamins add large chunks early, then stop helping.
FAQ
Mechanics questions
What is the Gen 1 Special stat?
A single number used for special attack and special defense. Electric, Fire, Water, Grass, Ice, Psychic, and Dragon attacks use it on both sides of the formula.
How do critical hits work in Yellow?
They key off base Speed. High-crit moves multiply the threshold; Focus Energy glitches and lowers it. Crits roughly double the level contribution in damage.
Why does Slash always crit?
High base Speed users push the high-crit threshold to the 255 cap, so Slash crits on almost every roll.
Should I use Focus Energy?
Not for crits. It reduces critical hit chance in Gen I. Skip it unless you are demonstrating the bug.
Do Pokémon gain EVs in Yellow?
They gain Stat Experience, the Gen I ancestor of EVs. The systems are related in spirit but not identical in numbers or caps.
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