Prompt: Postcard design suggestions (line drawing cartoon style, with calligraphy elements): Adventure map: It depicts the adventurous scenes of Yu Zijun crossing deserts and dangerous shoals and leading officers and soldiers to build the Great Wall. The line drawing emphasizes the outline, and calligraphy elements are added below, such as \"Top Gun\" and so on. Heroes assembled: Designing the scene where Yu Zijun summons soldiers and civilians can emphasize the image of holding a spear and high morale. The background is accompanied by the calligraphy font of \"Heroes Assemble\". Farmland and Castle: It depicts Yu Zijun farming with the people, with the farmland and castle in Yansui in the background. The bottom can be accompanied by calligraphy such as \"Farming is the way\". Border Guard: Depicting the scene of Yu Zijun and the army guarding the border at night, the tense military atmosphere can be expressed through the starry sky and bonfires. Calligraphy fonts such as \"Night Defense Frontier\" etc. Victory celebration: The scene where Yu Zijun celebrates with the officers, soldiers and people can have simple fireworks lines. The calligraphy below can say \"Happy Victory\". Friends outside the wall: The element of Yu Zijun shaking hands with the Mongolian leader is introduced, and the simple line drawing expresses the scene of friendly exchanges. Calligraphy font such as \"Neighbors share peace\". This design not only focuses on the cuteness of line drawing cartoons, but also adds calligraphy elements at the bottom to strengthen the artistic expression of historical figures and scenes. Students can further appreciate the charm of history by imitating and practicing calligraphy.

Prompt: Taking Yu Zijun, the builder of the Yan Sui Great Wall in the Ming Dynasty, as the theme, design a set of postcards for the museum. The overall style can be a bit cartoonish, and the target audience is students. Postcards can allow students to create paintings.