Summary

You have built from transistors a machine that draws by itself.

• Memory — a latch of two NOR gates, a D flip-flop of two latches: writing only on the clock edge.
• A counter — adding 1 in a column: XOR flips a digit, AND carries on.
• The raster scan — two counters visit the 4096 dots of the screen, like the beam of a TV.
• A fractal — the ten-gate rule (x AND y) = 0 draws the Sierpinski triangle.
• Chance — the LFSR and the chaos game: the same triangle from random dots; a half-way step is a shift.
• Animation — a frame counter and a comparison bring Munching Squares to life.

The finished machine is 3,064 transistors.

What next

"Worlds of Mandelbrot and Julia". On the same raster scan the circuit computes with fractions: multiplication, addition, comparison, an iteration counter. z = z² + c for every dot — and the Mandelbrot set appears on the screen. Change c with switches — and you get a Julia set: every position of the switches is a new world.