These overlays (sometimes known as bezels) display art on top of the game you're playing. To use them, you need a PC or Raspberry Pi (or other compatible system) running some version of MAME and the associated game software, as well as a widescreen (16x9) monitor mounted vertically. To display the overlay while playing a game, download the artwork file for that game overlay (it must have the same filename as the game), place it in the Artwork folder within your MAME directory and launch the game. (For instance, the software for the game Magic Sword is called msword.zip, so it requires a file in the Artwork directory also called msword.zip.)
All overlays are 4K resolution (2160 x 3840), and listed dimensions are for the game screen, relative to a 4K vertical monitor. The actual game screen size will depend on the resolution of your monitor.
Most of the overlays include multiple presets that let you choose the size of the game screen, access a "dark" version designed to look more like a dark arcade, and sometimes other options. To choose a preset, press Tab while running the game to bring up the MAME menu, select Video Options, and select a preset from the list.
Some overlays include Curved presets designed with a curved screen port, to better simulate the look of a CRT monitor. These presets work best if you are using a geometry shader that adds a curved look to the game screen. For an optimal experience, you may need to adjust your shaders to match the curvature of the screen shape in the overlay. If you are not using a geometry shader, you are using a shader that adds a curved bezel, or if you prefer a rectangular screen port, choose a Straight preset where applicable.
Technos' ambitious but relatively obscure beat-em-up Shadow Force contains a deceptive array of combat mechanics, making it more akin to a fighting game in many respects despite its side-scrolling levels and increasingly tough enemies and bosses. The game features a full six action buttons in the US release, which control high and low kicks and punches, jumping and the ability to possess enemies (the Japanese version has only three buttons and changes their commands, so check which version you're running). The latter ability is what really sets Shadow Force apart – when you activate the ability, you can inhabit many of the game's enemies, each of which has its own special abilities, adding a huge range of possible approaches to combat. Along with vibrant landscapes and sounds, it adds up to a challenging but memorable beat-em-up experience.