Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

grayscale image

An image storing one intensity value per pixel, with no color information.

A grayscale image stores one intensity value per pixel, an integer in $\{0,\dots,255\}$ at standard 8-bit depth, with $0$ pure black and $255$ pure white and no color information at all.