We can implement a day/night cycle similar to Pokemon Gold/Silver using just palette swap.

Using Usenti we can preview the color palette of our tilemap, and we can simply replace this palette and save a file with the new palette,

Then, using butano, we can load this new palette and replace the tilemap palette with few commands

to create:

const bn::bg_palette_item &night_palette_item = bn::bg_palette_items::night_palette;

to replace:

tilemap_palette.set_colors(night_palette_item);

this is the result:

That's it for today, but the next step is to be able to apply our fade in/out to this transition.