Anastacio said:
So this month I am looking to buy a Nintendo DSi and Pokémon Platinum. The last one I played in the series was Pokémon Red, so what new features am I in for?
Dark type
Steel type
Changes to resistances and weaknesses, e.g. Poison is neutral on Bug and Ice now resists Fire
Special is split into Special Attack and Special Defense
Moves are physical or special depending on the individual move instead of the type
Natures that give +10% to one stat and -10% to another
Pokemon abilities that are inherent or activate upon switching in
Pokemon gender
342 new Pokemon
Breeding
Trainer rematches
Gym leader rematches
A run button (after you get running shoes a few minutes in)
A bike with two speeds
Pokemon can hold items
Dozens of new moves
New functions or base power for some old moves, e.g. Roar and Whirlwind force a switch in a trainer battle and Dig has 60 power
Dozens of new items
Playable female trainer
Pokemon contests
92 TMs instead of 50, 8 HMs instead of 5
Weather conditions that affect battle
Other conditions that affect battle, e.g. Trick Room (for five turns, the slower Pokemon moves first) or Gravity (everything can be hit by Earthquake, evasion decreases)
New stones to evolve with
Pokemon can be moved to and from boxes without separate commands for withdraw and deposit
The option to use L as an A button equivalent
I could probably think of other things, but let's end it there. Suffice it to say you're in for a lot.
Edit: Haly is reaming me for neglecting to mention day/night! Edit 2: And the ability to make an underground base. And mining for fossils and evolution stones in a minigame. Edit 3: And online.