To understand POWDER, you should first understand roguelikes. “Roguelike” is a term applied to a wide variety of games which share a common inspiration from the game Rogue. A non-exhaustive list of such games would be: ADOM, Nethack, Crawl, Diablo (I & II), Moria, and Angband.

Powder is not a port of an existing roguelike. It is built around replayability and long term ergonomics, not short term learning. It uses actual graphic tiles (16×16) rather than the traditional characters.

Changes:

Releasing a possessed creature on the otherside of a dimensional portal should no longer cause problems.
Releasing possession after your body has died but left a corpse will no longer leave you as some weird ghost. This also prevents you from picking up your own corpse and eating it, which has dire reprecussions.
Releasing possession after your body is a statue is likewise fixed (JCM)
If you polymorph and drop something on the ground due to lacking space and that item merges with an existing item, it no longer crashes.
New tridude rooms have a unique tridude to act as the leader to avoid infighting.
Zapping a wand of create trap outside of the map no longer crashes.
Rays bouncing off the map boundaries no longer risk crash.
You can read equipped scrolls, books, and zap equipped wands and drink equipped potions. No particular advantage is currently conferred by such, other than looking cool, but it seemed odd you had to unequip things to do this. (Bill Walker)
Starting inventory has been normalized and you start the game wearing your armour and weapon. Your bonus item may still be better, so you likely still want to look in your inventory at the start. This means no more starting the game with an evil -2 floppy had and dagger, but also no more starting with a +3 holy artifact warhammer. (David Damerell, Richard Quirk, Stu)
Dying while possessing a creature and being on a different level from your body will no longer corrupt the mob list of your old level.
Zapping a wand of teleport at yourself and dying after the teleport will no longer crash.
Zapping a wand of teleport at yourself will no longer teleport items on the square you teleport *to*, and instead teleport them from the square you teleport *from*.
Quit & Save will immediately put you at the main menu rather than letting you spy on the local dungeon life. (Clare Boothby)
Help and tutorial docs now talk about how to use the stylus/mouse.
[SDL], [DS]: Starting image now fills the screen. It has also been made darker as the original image was calibrated against the original GBA.
[SDL]: Linux and Windows users will find their screen size a bit larger to bring it in line with the DS screen. There is method to my madness.
The title menu now has an Options choice that lets you change the options and read the help without starting a game.

http://www.zincland.com/powder/index.php?pagename=release