Visualizes measurability (preimages of measurable sets) using a blocky domain X mapped by f into codomain Y, highlights the preimage f^{-1}(B) for a moving measurable set B, shows sigma-algebra closure cues (complement/union), and animates the Lebesgue integral construction from indicators to simple functions to limits and signed functions, with mu(A) displayed as a filling measure bar.
Pure Canvas2D; responsive scaling via scale=min(w,h)/240 and 6px grid snapping for a retro block aesthetic. Uses a 4-step 4.2s cycle with easing to highlight (1) indicators, (2) simple functions, (3) monotone limits, (4) signed decomposition. A lightweight particle burst suggests countable unions; all colors are GREEN/GREEN_DIM on black.