Filling up

An SSD1306 128×64 OLED (0x3C, SDA/SCL, 3.3 V). Switch it on blank at the start, then fill it from the top, one full-width band 8 pixels tall every second: after 1 s rows 0–7 are lit, after 2 s rows 0–15, … after 8 s the whole screen. Then keep it full.

Tip: oled.fill_rect(x, y, width, height, 1) and oled.show().