A vivid and colorful illustration depicts thousands of people dressed in different colors celebrating in front of a towering skyscraper square, forming an extremely dense crowd pattern with clear facial features. The background is a huge city square, creating an infinite sense of vastness, with each person holding a red gift box with their back to the screen. The wide-angle design creates a surreal effect, capturing the essence of the celebration with bold and clear line art.

Poster design, pastel and bold colors, minimalist and flat style, cute ink and flat colors, icons of birthday party symbols, including: sun, birthday cake, candle, heart, colorful flags, flower, balloon, gift box, party hat, sunglasses, with the title 'Happy Birthday', cute stickers, bold color palette.