freerice.com

There's a test-your-vocabulary game at freerice.com which is free to play and if you get correct answers then the sponsors give 20 grains of rice to the world's poor. It has the World Food Programme's approval. You are graded and can move up to level 55 which is, like, language black belt. It claims people rarely get beyond level 48, but I bet some hermit has attained level 55 perfection despite only eating figs.