一张万圣节笑话海报，标题为“Boo-ology!”，回答关于幽灵的谜语，风格俏皮可爱的卡通。奶油色圆润字母带橙色描边和3D阴影，上下堆叠排列，下方是背着橙色书包、手拿紫色书本的微笑幽灵，身处有南瓜和蝙蝠的绿色教室。可换成你自己的谜语和答案，制作笑话卡片或教室标牌。

Create a finished square Halloween joke card for school, designed to remain readable as a small printed card or phone image. Use a bright, friendly children’s picture-book illustration style with crisp shapes, soft dimensional shading, and a warm classroom scene. Keep all artwork and text inside a generous 8% safe margin. Render only these two lines, spelled and punctuated exactly, with no other lettering anywhere: setup first, “What is a ghost's favorite subject?”; directly beneath it, the punchline “Boo-ology!” Make the setup a clear, single-line tier and the punchline the largest, boldest type on the card. Draw the letterforms as custom chunky, rounded display lettering with wide counters, open apertures, sturdy strokes, and even spacing; use bright ivory fills, saturated orange and teal outlines, and a subtle offset shadow. Keep every letter crisp and unobscured. Place the two text lines across the upper half, centered and separated by clear breathing room. In the lower half, show one smiling, sheet-shaped ghost wearing a small orange backpack, standing beside a classroom desk with a few colorful books and a simple chalkboard. The ghost gestures toward a floating book with tiny friendly bubbles shaped like little ghosts; no lettering or symbols on the chalkboard, book covers, or props. Keep the illustration clearly separate from the joke text. Use pumpkin orange, teal, violet, ivory, and a pale mint classroom background; add a few small star and bat silhouettes as sparse decoration. Soft even lighting, clean edges, no gore, no frightening details, no extra jokes, no logos, no border text, no watermark.