I know you’re probably joking but Gimp has neither shape tools nor Vector Layers.

The secret ingredients are setting up a grid and resizing to work at a high resolution, turning on snap to grid, using the brush tool by clicking then holding shift then clicking again to create a line, fill tools, and using a very large brush followed by the same brush at the same point but smaller, and lastly the copy/paste, mirror, and rotate tools to create symmetrical or circular patterns.

Tbh its pretty time consuming but very simple to do.