ArduinoGl how to prevent from flickering polygons


Hi i developing game on Arduino. I found library named ArduGl i downloaded installed it. When i try cube example on my 1.8 inch tft spi display vertex colors starts to flickering . Why this happens i think arduino’s low ram but how to fix and how to opitimize with arduino.
I know ardu gl is unofficial opengl wrapper for Arduino but code and system is same. Logic is same.
If someone wants the library: