Wet the watercolour paper all over with the large flat brush dipped in clean water. The paper should look shiny. While it is still wet, drop large washes of purple and blue paint across the whole surface, letting colours bleed into each other. Work quickly: you want the colours to flow and merge rather than sitting in separate patches.

While the paint is still wet and shiny, scatter table salt generously over the surface. The salt immediately starts pulling pigment, creating pale spidery bursts. Children can do this step themselves; it is satisfying and low-risk. Leave the paper completely flat to dry for at least 45 minutes. Do not tilt it or touch the salt.

Once fully dry, brush the salt off gently with your hand over a sink. The starbursts stay in the paper. If you try to brush off the salt before the paint is bone dry, the effect smears.

An adult draws a simple sitting-cat silhouette on the black card: a rounded body, a tail curling around the base, two pointed ears and a round head. Cut it out carefully. The silhouette should be about 10 cm tall to fit neatly on the A4 background.

Glue the cat to the lower centre of the dried watercolour background. Use the fine brush to add a tiny crescent moon in yellow or white paint in the upper right corner if there is space. Leave the glue to set for 10 minutes.