Alright, so, I'm making a letter detailing the major mechanical changes that occurred between each generation, so current gen players can pick up on key differences and have an easier time learning past gens. Similarly, past gen players could check it out in reverse to learn up on how the game's mechanics have changed over time should they wish to learn BW. Stuff like a move's Base Power, accuracy, or a slight change in how an ability works probably won't be included, though competitively relevant move mechanics (RBY Hyper Beam, BW Explosion nerf, etc.) should be listed. I'm compiling this mostly from memory, so I'm sure I'll be missing shit, which is where you all come in. Let's try to fill in any cracks here to make this as all-encompassing as possible~ Changes from BW to DPP A Pokemon's sleep counter does not reset when switching out. Also, sleep lasts for 1 to 4 turns rather than BW's 1 to 3. The moves Explosion and SelfDestruct temporarily halves the opponent's Defense, effectively doubling their Base Power. Wish heals the target by 50% of its HP, rather than 50% of the user's HP. The trapping effects of Mean Look can be Baton Passed. Taunt lasts for 2 to 4 turns. Encore lasts for 3 to 7 turns. Changes from DPP to ADV All Dark, Dragon, Electric, Fire, Grass, Ice, Psychic, and Water moves are special moves. All Bug, Fighting, Flying, Ghost, Ground, Normal, Poison, Rock, and Steel moves are physical moves. Sleep lasts for 1 to 6 turns. When the faster Pokemon faints, the opposing Pokemon does not get to move. Taunt only lasts for 2 turns. Encore lasts for 2 to 6 turns. Counter and Mirror Coat treat Hidden Power as physical, regardless of type. Changes from ADV to GSC IVs range from 0-15 rather than 0-31. A Pokemon can have 255 EVs in every stat. Natures and Abilities do not exist. If a badly poisoned Pokemon is switched out, it will be afflicted with regular poisoning. If a burned or poisoned Pokemon KOes its opponent, it will not take burn or poison damage that turn. A frozen Pokemon cannot attack on the turn it thaws out. If Sleep Talk chooses Rest, the Pokemon will regain all of its health and have its sleep counter reset. If Sleep Talk chooses Roar or Whirlwind and the user is faster than the opponent, it will fail. Phazing moves, Counter, and Vital Throw must go second in order to succeed. Only one layer of Spikes can be set. Changes from GSC to RBY Rather than Special Attack and Special Defense stats, Pokemon simply have a Special stat that functions as both. Items do not exist. Sleep lasts for 0 to 6 turns. Also, a Pokemon cannot attack on the turn it wakes up. A Pokemon using Rest will wake up after 2 turns rather than 3. If a Pokemon uses Rest while burned or paralyzed, it will retain the respective Attack or Speed drop until switching out. If a Pokemon uses an Attack or Speed boosting move while burned or paralyzed, respectively, the drops will be removed and the stat will raise as if no status was inflicted. The probability of critical hits is determined by base Speed. The formula used is %CH = Base Speed x 100/512. Critical hits ignore all stat changes for both Pokemon, as well as the effects of Light Screen and Reflect. Bug is super effective against Poison and has normal effectiveness against Ghost, Poison is super effective against Bug, Ghost has no effect against Psychic, and Ice has normal effectiveness against Fire. If a Pokemon KOes an opposing Pokemon or breaks a Substitute with Hyper Beam, it does not have to recharge the next turn. A frozen Pokemon will not randomly thaw out. The accuracy and critical hit rate of all moves is reduced by 0.4% (except Swift, which will never miss). A poisoned or burned Pokemon loses 1/16 of its health rather than 1/8. Similarly, Leech Seed drains 1/16 of health rather than 1/8. A Pokemon hit by a partial trapping move cannot attack for the duration of the attack. However, it can switch out of the partial trapping move. Steel and Dark do not exist as types. Night Shade and Seismic Toss hit everything, regardless of type. If Explosion or SelfDestruct is used against a Pokemon behind a Substitute and breaks the Substitute, the user will not faint. Roar and Whirlwind have no effect. Haze removes major status conditions from the opponent. Horn Drill, Fissure, and Guillotine will always fail if the opposing Pokemon has higher Speed.