Mega Man 4 is a platforming game for the Nintendo Entertainment System.

The game starts with the backstory of the original game as well as this one, which is a nice touch since Mega Man 1 had no such opening story sequence. Just like before, our hero must defeat eight robots, along with the mad scientist who created them...only this time it's apparently a different mad scientist!

As always, when you beat a Robot Master, you gain its weapon. Each Master is weak against one of the others' weapons. Additions from the previous entries are back, like energy tanks, Rush the robo-dog, and the ability to slide.

A welcome new feature is the ability to charge your main weapon, which gives you a slight edge if you haven't yet obtained a particular boss's weakness. There are two new support items: the balloon and the wire. The balloon lets you create floating platforms to jump onto (just like Item 1 in Mega Man 2) and the wire latches onto the ceiling and pulls you upward. They seem a little unnecessary since Rush is still present, but they give you more options to tackle any situation.

A password system is an added feature and lets you continue after defeating the 8 Robot Masters.

The Japanese version of Mega Man 4 has an unused tile in the title screen graphics that perfectly fits into the black space at the bottom corner of the helmet's ear. This patch uses this tile for its intended purpose.

This patch also fixes some probable mistakes and regressions from previous games:
-Correct Roll's face palette when the screen turns sepia (part of her skin was eye-colored)
-For the ending, add a pixel of hair by Mega Man's neck (match Mega Man 2)
-For Mega Man's run sprites, add back part of his shoulder and layer his face so it is under his arm (match Mega Man 1 and 2)
-Fix Rush's menu animation so his back leg bends instead of using a duplicate tile of his standing leg (match Mega Man 3)

Database match: Mega Man 4 (USA)
Database: No-Intro: Nintendo Entertainment System (v. 20210216-231042)
File SHA-1: 2AE9A049DAFC8C7577584B4B9256F7EF8932B29C
File CRC32: ADBD4E48
ROM SHA-1: 673A888C468ABE33FB0B3F063C6837DD21D5D32B
ROM CRC32: 2BC67AA8

Database match: Rockman 4 - Aratanaru Yabou!! (Japan)
Database: No-Intro: Nintendo Entertainment System (v. 20210216-231042)
File SHA-1: C33C6FA5B0A5B010AF6B38CBD22252A595500A5A
File CRC32: 771A9138
ROM SHA-1: 83F5EA60D6E6489EC0E5AF4B938D2D1C8FD24DD5
ROM CRC32: F161A5D8

Database match: Mega Man 4 (Europe)
Database: No-Intro: Nintendo Entertainment System (v. 20210216-231042)
File SHA-1: BD607BE30AF655A2F171A45E1588B5EEC45E2FAE
File CRC32: 9DE81F0A
ROM SHA-1: 8F6E3D7145E7856EAEC1BC1F195DF30631425C0E
ROM CRC32: 1B932BEA