About the Terrain effect
Terrain draws a side-on landscape. For each column, two slow sine waves of different lengths are added to find the height of the ground, producing gentle hills with occasional larger swells. Below the ground line, cells are filled with the shading blocks ░▒▓█, getting denser with depth, so the surface has a light crust and the earth beneath looks solid. Over time the waves drift in opposite directions, so the hills slowly change shape and the landscape seems to scroll past, like the view from a train or the parallax backdrop of an old side-scrolling game. The upper half of the screen stays mostly clear for titles or text. Green gives grassy hills, amber a desert at sunset, white a snowy ridge. Combine a slow speed with a large font size for a chunky, pixel-art style horizon.