Thanks for this great piece of code
Here is a Lite-C version of it:
Code:

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//simple freeflight without collision detection
void tools_camera_freeflight1()
{
	var tools_movespeed=20; //how fast to move
	var tools_movecam[3];

	while(1)
	{

		//turn the camera
		camera.pan -= mouse_force.x*15*time_step;
		camera.tilt += mouse_force.y*15*time_step;
		camera.tilt = clamp(camera.tilt,-90,90);

		vec_set(tools_movecam[0],nullvector); //reset movement vector

		//ket wasd or cursor movment
		if(key_w||key_cuu){tools_movecam[0] = tools_movespeed*time_step;}
		if(key_s||key_cud){tools_movecam[0] = -tools_movespeed*time_step;}
		if(key_a||key_cul){tools_movecam[1] = tools_movespeed*time_step;}
		if(key_d||key_cur){tools_movecam[1] = -tools_movespeed*time_step;}

		//rotate by camera heading
		vec_rotate(tools_movecam[0],camera.pan);

		//move the camera
		vec_add(camera.x,tools_movecam[0]);

		wait(1);
	}
}

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