test showing how frame based motion can be problematic

varfps.c

/*******************************************************************************************
*
*   raylib [core] example - Basic window
*
*   Welcome to raylib!
*
*   To test examples, just press F6 and execute raylib_compile_execute script
*   Note that compiled executable is placed in the same folder as .c file
*
*   You can find all basic examples on C:\raylib\raylib\examples folder or
*   raylib official webpage: www.raylib.com
*
*   Enjoy using raylib. :)
*
*   This example has been created using raylib 1.0 (www.raylib.com)
*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
*
*   Copyright (c) 2013-2016 Ramon Santamaria (@raysan5)
*
********************************************************************************************/

#include "raylib.h"

int main(void)
{
    // Initialization
    //--------------------------------------------------------------------------------------
    const int screenWidth = 800;
    const int screenHeight = 450;

    InitWindow(screenWidth, screenHeight, "raylib [core] example - basic window");

    Vector2 pos = { 10, 50 };
    bool useTime = true;
    float speedTime = 100;
    float speedFrames = 2;
    float dir = 1;
    
    //--------------------------------------------------------------------------------------

    // Main game loop
    while (!WindowShouldClose())    // Detect window close button or ESC key
    {
        SetTargetFPS(GetRandomValue(30, 120));               // Set our game to run at 60 frames-per-second

        if (IsKeyPressed(KEY_SPACE))
            useTime = !useTime;

        if (useTime)
        {
            pos.x += speedTime * GetFrameTime() * dir;
        }
        else
        {
            pos.x += speedFrames * dir;
        }

        if (pos.x > 780 && dir > 0)
            dir = -1;
        if (pos.x < 10 && dir < 0)
            dir = 1;

        BeginDrawing();

        ClearBackground(RAYWHITE);

        DrawCircle(pos.x, pos.y, 10, RED);

        DrawText("Press Space to Toggle Mode", 60, GetScreenHeight()-20, 20, LIGHTGRAY);
        DrawFPS(0, 0);
        DrawText(useTime ? "Using Time" : "Using Frames", 120, 0, 20, BLACK);

        EndDrawing();
        //----------------------------------------------------------------------------------
    }

    // De-Initialization
    //--------------------------------------------------------------------------------------
    CloseWindow();        // Close window and OpenGL context
    //--------------------------------------------------------------------------------------

    return 0;
}