// camera vars to fill out
mat4 view, proj

updateViewProj() // compute proj matrix and view matrix (when needed), you could write a separate updateViewMat and updateProjMat, if you like

updateProjMat() // sets up proj and aasumes canonical camera is at the origin and looking down the -z axis

updateViewMat() // sets up view and is affected by moveLeft, moveRight, moveForward, and moveBackward

Lets focus on updateViewMat, and on moveForward for the "ground view"

One option is to have the below used for all move* functions

float camRot; // camera rotation about the y-axis
vec3 camPos;  // camera position

moveForward()
	smallStep = rotateAroundY(camRot) * vec3(0,0,-1*stepSize)
	camPos = camPos + smallStep;
	
moveBackward()
    ...
	
moveLeft()
    ...
	
moveRight()
    ...
	
	
updateViewMat()

// use camPos and camRot, and a small "look down rotation" to create view
// you must implement any needed rotate/translate matrices (e.g., use 4x4 matrices to incorporate both rotations and translations)
// recall that if you have 4x4 matrixes, then you will multiply them by 1x4 vectors, and divide by w

// xform order matters: https://www.youtube.com/watch?v=CmgSye6-Ack