Improve loop with fps control

include/window/window.h

@@ -341,8 +341,7 @@ public:
 
   // Time
 
-  uint64_t get_time();   // returns the time in nanoseconds since the window was created
-  uint64_t delta_time(); // returns the time in nanoseconds since the last render call
+  uint64_t get_time(); // returns the time in nanoseconds since the window was created
 
 private:
   // internal data and functions