Cream the butter and sugar with an electric mixer until pale and fluffy, about 3 minutes.

Beat in the egg and vanilla, then gradually add the whisked dry ingredients. Mix until a soft dough forms. Wrap and refrigerate at least 1 hour.

Preheat oven to 350°F (175°C). Roll the dough to ⅓‑inch thickness, cut into squares, and arrange on parchment-lined baking sheets.

Bake for 10 to 12 minutes until the edges are lightly golden. Cool on the sheet for 5 minutes, then transfer to a wire rack.

Cool completely, then outline and flood each cookie with tinted royal icing. Let the base dry, pipe on pixel details, and set for 2 to 3 hours before serving.