A vibrant cartoon with colours and smooth animation. Create a colorful, cinematic 3D cartoon short film for children. Main character: A cute, curious 8-year-old boy named Leo, with messy brown hair, big expressive brown eyes, a yellow hoodie, blue shorts and red sneakers. Keep his appearance consistent in every scene. Story: Leo discovers a tiny glowing blue door hidden inside an old tree in a magical forest. When he opens the door, he enters a miniature world where everything is alive. He meets a funny little green dragon named Momo who can breathe bubbles instead of fire. Momo is scared because his magical crystal has disappeared. Leo and Momo search the magical forest together. They cross a sparkling river, walk through a field of giant flowers, and discover a mysterious cave. Inside the cave, they find the crystal guarded by a huge but friendly stone creature. Leo realizes the creature is not dangerous and politely asks for the crystal. The creature gives it back after Leo helps repair its broken stone heart. At the end, Momo returns the crystal to his village and the entire magical world lights up with colorful glowing lights. Leo says goodbye to Momo and returns through the tiny door. Before closing the door, Momo gives Leo a small glowing blue crystal as a gift. Visual style: high-quality 3D animated cartoon, colorful environments, soft cinematic lighting, expressive facial animations, cute character design, detailed backgrounds, magical atmosphere, family-friendly, playful and adventurous tone. Animation: smooth character movements, natural walking and running, expressive gestures, accurate lip synchronization, dynamic camera movements, cinematic close-ups, wide establishing shots and gentle transitions. Keep Leo and Momo's character design, clothing, colors and proportions exactly consistent throughout all scenes. Aspect ratio: 16:9. Duration: approximately 3-5 minutes. No text, no subtitles, no watermark.