Like many retro games, Zelda II has its fair share of bugs and glitches – one of which involves pressing left and right at the same time to dash through levels, including locked doors.
This 'acceleration' glitch is detailed in this excellent video, but is practically impossible to do on original hardware, as you can't press both directions at the same time on the NES controller.
Thankfully, Robert Dale Smith has created an accessory which makes this glitch possible on your NES. The 'NES Uni Tap' is made up of two NES extension cords, two Schottky diodes and a 4.7-ohm resistor, and allows you to connect two controllers to the same port on the console.
The end result is that it's now possible to press left and right simultaneously, so the acceleration glitch is now possible outside of emulation:
We'd imagine there are other uses for this device, too – if you can think of any, post them in the comments section below.