Gremlins 2 is a game for the NES, based on the movie with the same name. There is no Gremlins 1 game for the NES, however some Atari consoles recieved them.
Useful RAM addresses
Major/minor indicates a 16-bit value. The "major" value is multiplied by 256 (240 in the case of the Y-coordinate) and the "minor" value is added to that.
(paraphrased from the TAS submission)
Movement: Gizmo always moves at 1.5 pixels per frame, no matter what direction. This means zig-zagging is just as fast as walking straight.
Stage finish boost: After finishing a stage, you can walk around while the music is still playing. The way Gizmo is facing when the music stops will give a 1 frame boost in that direction in the next stage.