Mama Soybean's Delicious Oyster Sauce

From the author: Mama Soybean's Delicious Oyster Sauce is a small puzzle game for MS-DOS. It has 16 levels, stupid background story and clumsy DOS-era gameplay with eye-hurting CGA graphics. Known bug: If you reach the level 16 without using passwords, the game will crash after the level 15 with message "File not found". Workaround: write down the password of floor 15, reset the game, choose "Password", input the password and now beat the stage 15. Map 16 should load normally now.