A generative map of imaginary terrain. Every seed grows a new landscape of elevation lines. Drag on the canvas to raise hills, tune the sliders, and save the ones you like as PNG.
Tip: drag to raise a hill, hold Shift (or use two fingers) to carve a valley. Press R for a new seed, S to save.
Elevation comes from layered value noise (fractal Brownian motion): several octaves of smooth random noise, each at double the frequency and a fraction of the amplitude of the last. The roughness slider sets how many octaves are stacked. Contour lines are traced with the marching squares algorithm, which looks at each grid cell's four corners and draws the segment where the terrain crosses a given height. Your brush strokes add Gaussian bumps on top of the noise before the lines are traced.