「Sustainable」は FontVibe AI で作成したレインボーの文字エフェクトです。鮮やかな多色レインボーグラデーションの文字エフェクトです。滑らかな色の移り変わり、プリズムのような光、そして陽気で色彩豊かなタイポグラフィが特徴です。

rendered as rainbow text effect — COLOR (mandatory): each individual letter must contain a complete ROYGBIV rainbow gradient top-to-bottom within itself — top=red, upper=orange, mid=yellow-green, lower=blue-indigo, bottom=violet. NOT one color per letter. NOT a gradient across the whole word. Every letter is its own complete rainbow. Full chroma Pride flag saturation — not pastel, not muted, not shifted to any single hue. YouTube thumbnail format (16:9): 'Sustainable' as rainbow candy balloon letters as the thumbnail text overlay. Background: dramatic night cityscape with bokeh city lights — dark sky, colorful city glow from below. Each letter: maximum spherical inflation, complete ROYGBIV rainbow gradient, ultra-glossy candy lacquer, brilliant specular highlights. The rainbow 3D balloon letters are sharp and vivid against the dark city background — maximum clickability, impossible to miss in YouTube search results.