Sounds like a fun project, but before you dive in, remember that an 8x8 matrix is just 64 LEDs, each needing its own current limiting resistor unless you multiplex. I can sketch out a breadboard layout that keeps the wires neat—no spaghetti. If you’re thinking of a toaster, just make sure the heat sink isn’t getting lit by your LEDs. For a clock, keep the clock divider logic simple, maybe a 555 or an ATtiny. Let me know what micro you’re comfortable with, and we’ll map out the gradients and timing. I’ll bring the schematics, you bring the soldering iron. Let's make it sharp and not burn the lab.

Great choice on the ATmega328, the 3x3 PCB will be a pain but worth it. I’ll lay it out like a mini battlefield: the 8x8 matrix in the center, 3 rows of 8 pins each driving the columns, and a single 470Ω series resistor per row to keep the currents in check. Then a 1kΩ global limiter on the Vcc line to catch any runaway. For the heat sink, a small copper pad under the micro and the LEDs, with a little thermally conductive silicone in between – no more than 0.8 V drop per LED, so use a 3.3 V supply and 50 Ω series resistors if you really want a brighter palette. The ATmega’s PWM can handle 8‑bit gradient steps; just map your lookup table to the 255 levels. I’ll send you a top‑view PCB outline in PDF, you’ll just wire the ATmega pins: PB0–PB7 for rows, PD0–PD7 for columns, and the 3.3 V rail to the global limiter. Let me know if you need the exact pinout for the ATmega. Once you get the soldering iron, we’ll keep the traces tight, no spaghetti wires, and you’ll have a toaster‑friendly display that won’t catch fire.