DOOM on the Casio Loopy, the Japanese console from 1995 Made for Girls

In the ever-growing list of devices capable of running DOOM, one of the most improbable consoles ever produced makes its entry: the Casio Loopy, a Japanese machine from 1995 designed for a female audience and left on the margins of gaming history. Throughout its entire life cycle, which ended with the cessation of hardware production in 1998, the Loopy saw only eleven titles released, none of which was the shooter from id Software. This was remedied by the developer known as Throaty Mumbo.

The project, dubbed LoopyDOOM, utilizes the authentic engine and not a ground-up rewrite: the DOOM from id Software passed through PrBoom and the conversion for Game Boy Advance GBADoom, with a new hardware layer written for the video chip, timers, the pad, and audio of the Loopy. The author describes it as somewhat unpolished, in line with what is a technical demo.

Six Maps and 8-15 Frames Per Second

The heart of the console is an Hitachi SH-1 at 16 MHz, big-endian and lacking division instruction, alongside about 512 KB of RAM. However, the most stringent limit is the memory space: the original 2 MB of ROM, increased to 4 MB by the Floopy Drive cartridge necessary for running on real hardware, suffices for six maps, from E1M1 to E1M6 of the first episode. The performance is around 8-15 frames per second, with a low resolution due to the code still being unoptimized.

MIDI Music, Effects on a Second Chip, and Thermal Printing

The audio part is the most intriguing. The music is true MIDI: the tracks from DOOM, in MUS format, are decoded and routed to the Loopy's uPD937 synthesizer, whose presets are proprietary to Casio and not the General MIDI standard, so the instrument pairing was chosen by ear, track by track. The chip ignores the dynamics of notes and has a rather weak output, a trait of its analog stage that no software can correct.

Sound effects could not come from the same chip, which lacks a PCM path: the SH-1 sends short commands via serial to an RP2040 mounted on the cartridge, which mixes eight voices of DOOM's PCM samples and plays them through an external DAC. Therefore, in addition to the cartridge, a dedicated firmware and some wiring are required; otherwise, the game remains silent except for the music.

The most entertaining touch comes from another native feature of the Loopy, which among its peculiarities had an integrated thermal printer for stickers. From the options menu, you can print the current frame on paper: a physical screenshot of your battles, provided the printer does not jam.

Potential recipients are very few: estimates indicate a few dozen units still in circulation, and to operate it you need the Floopy Drive and its flashing tool. Those who do not own one and want to experience the thrill can instead opt for the LoopyMSE emulator, where the code runs even faster than on the original console.