Patterned Sponge Cake

This was a trial attempt for a patterned sponge cake. It's made with a very light batter, small portions are colored and piped into the design on the bottom, chilled, and then un-tinted batter spread on top before baking.

I think it's not bad for a first attempt, and I freehanded the design, which could have used a bit more planning. Any advice or suggestions on improving for future attempts? I had difficulty with the designs spreading a bit and they didn't turn out as sharp as I'd have liked. I LOVE the concept and the way it really visually elevates a simple cake and allows the flavors to shine without being overwhelmed by frosting. I did a lemon sponge for this one - filled with a stabilized whipped cream and lemon curd.