overall, the mosque's architecture combines a traditional chinese architectural form with islamic functionality. for example, whereas traditional chinese buildings align along a north–south axis in accordance with "feng shui", the mosque is directed west towards mecca, while still conforming to the axes of the imperial city. furthermore, calligraphy in both chinese and arabic writing appears throughout the complex, sometimes exhibiting a fusion of styles called sini, referring to arabic text written in chinese-influenced script. some scholars also speculate that the three-story, octagonal pagoda in the third courtyard, called the "shengxinlou" or “examining the heart tower,” originally served as the mosque's minaret, used for the call to prayer.