Database: card_games
Question: What is the percentage of the set of cards that have Chinese Simplified as the language and are only available for online games?
SQL: SELECT CAST(SUM(CASE WHEN T2.language = 'Chinese Simplified' AND T1.isOnlineOnly = 1 THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(*) FROM sets AS T1 INNER JOIN set_translations AS T2 ON T1.code = T2.setCode