Sally Acorn in Sonic the Hedgehog (aka Sally in Sonic 1) is a fan-made ROM of the game Sonic the Hedgehog for the Sega Mega Drive/Genesis, with Princess Sally Acorn as a playable character in place of Sonic the Hedgehog.
The game was modified by Sonic Retro member E-122-Psi, with additional programming and coding by other members including Snkenjoi,MarkeyJester, Aquaslash, Selbi and Hayate.
Sally is slower than Sonic and can't use spin attacks; however, she has a number of stealth and agility-based abilities to compensate and access areas Sonic had difficulty reaching, as well as the use of handheld device NICOLE:
NICOLE Laser Attack: Press A and Sally uses NICOLE to fire a small projectile which hits nearby enemies and obstacles. NICOLE Scan Mode: Press B and NICOLE will send a data wave to reprogram monitors and other Eggman traps. NICOLE Downward Laser: Press Down + A/B while airborne to fire at objects straight below. Sally also gets a small vertical boost. Slide: Press Down while running to slide on the ground for a short distance. Sally can also slide under certain obstacles using this method. Somersault Dash: Press Down + B/C while on the ground and Sally will somersault forward at a high speed. This is useful for jumping long distances.