In this video from Youtuber Kaseo, we get a demonstration of his PK-303, a Roland TB-303 inspired bassline synthesizer that takes on the form of Pikachu.
The PK-303 makes use of x0x-heart, a chip that replicates of the sounds of the original TB-303 and can be implanted into any DIY synthesizer.
The x0x-heart is the heart of the infamous TB-303, surgically extracted to be transplanted into your designs. The x0x-heart is just the analog section of the TB-303, replicated with SMT components, and made small enough to fit into a Eurorack modular format. It even has a Eurorack power header on it.
As you can hear in the video, the x0x-heart does an incredible job in creating the acid basslines that are reminiscent of the TB-303 bassline synthesizer. You can visit the x0x-heart website to learn more about the open-source chip.