Prompt vocabulary matters more than prompt quality & other lessons from generating 400 game sprites overnight

Spent the last few weeks building an AI image pipeline to generate ~400 assets (unit sprites, icons, terrain tiles) for an open source Ci game as part of my job. Sharing the specific failure modes because a few of them were genuinely non-obvious. The thing that surprised me most: exact phrasing unlocks entirely different model behavior I needed sparse tint overlay masks. These are images where only certain pixels are colored, showing where team colors appear on a sprite. Every reasonable prompt produced solid silhouette fills. "Color masks," "tint layers," "overlay maps" - all solid fills.