I have fond memories of soldering my own small Blinkenlight, a BlinkenLED, around 2005 as a kid. This was before the Raspberry Pi was around - it was just a 10x20 LED matrix controlled by 20 shift registers [0], connected to the serial port of an old DOS laptop. I remember that it was trivial to shift the individual bits through the serial port with a small BASIC program.
Soldering this thing, however, was a challenge. It was basically 200 LEDs on a perfboard, the cathodes all connected by a continuous strip of non-isolated wire (I think I used paper clips for that), and the anodes all individually connected to the shift register output pins via flexible wires. It took me several weeks to finish this with a cheap 10 EUR soldering iron from my local hardware store, and it did not look nice from the back.
It worked very reliable, however, and I used it to display the time, the date and some small animations for some years.
Soldering this thing, however, was a challenge. It was basically 200 LEDs on a perfboard, the cathodes all connected by a continuous strip of non-isolated wire (I think I used paper clips for that), and the anodes all individually connected to the shift register output pins via flexible wires. It took me several weeks to finish this with a cheap 10 EUR soldering iron from my local hardware store, and it did not look nice from the back.
It worked very reliable, however, and I used it to display the time, the date and some small animations for some years.
[0] https://en.wikipedia.org/wiki/Shift_register