A rhetorical question: if you have never played Karateka it’s worth doing it. You can google for the karateka.dsk.gz file and load it into the AppleWin emulator.

There is a DOS version, but, unfortunately, the gameplay was slightly changed. In the Apple’s version the opponents inside the house never approach you first. There was a trick: a little step towards and immediately step back. This was the only way to force them to attack you. Then you can low-kick them. In the DOS version they always attack first, so just low-kick.

But for the DOS version there is a magic patch allowing to speedrun the game.

Immortality
KARATEKA.EXE
00003066: 48 90
00003D7E: 48 90

Steel breast
KARATEKA.EXE
0000306E: 83 C6
0000306F: 3E 06
00003072: 3F 01
00003073: 7E 75

Flying kick for humans
KARATEKA.EXE
00002F30: 7E 00

Flying kick for bird
KARATEKA.EXE
00002E2F: 7F 00
00002E30: 01 00
00002E34: 3D 25
00002E35: 04 00
00002E44: 06 00

Kill bird by first kick
KARATEKA.EXE
000031BA: 85 33

Kill humans by first kick
KARATEKA.EXE
00002F3A: 85 33

For example:

Don’t miss at the end when the princess hopelessly kicks you when you approach in the stance.

P.S. Unfortunately, the sources of this spectacular game are still closed.