"A vibrant and adventurous thumbnail for a YouTube video titled

"A vibrant and adventurous thumbnail for a YouTube video titled 'The Mystery of the Hidden Treasure.' The image should feature four young boys in a school setting, each with an expression of excitement and curiosity. The boys are holding a treasure map and a key, standing in front of a large, old chest that is slightly open, revealing colorful books, puzzles, and games inside. The background should depict a dimly lit, mysterious classroom with shadows, emphasizing the treasure hunt theme. The title 'The Mystery of the Hidden Treasure' should be prominently displayed in bold, playful fonts at the top, with elements like a magnifying glass, treasure chest, or map integrated into the design. The overall style should be colorful, engaging, and appealing to children."