I bought the full version for practicing TOPIK exam, but after few days, you removed the function of explain mistakes. Which changed the original function to a forced purchase. So take my money back. You are a liar. 購買永久解鎖所有功能，使用約一個月後，突然錯題不再給解釋說明，強迫要購買訂閱高級解釋說明，今天早上更誇張，連進入APP都不行了。 我要主張退款。