:: process-keys ( g -- )
    read-keyboard keys>> :> keys

    key-w keys nth
      [ g 0 >>angle-diff drop ]
      [ ] if

    key-e keys nth
      [ g 1 >>angle-diff drop ]
      [ ] if

    key-h keys nth
      [ g [ 1 + ] change-horiz-angle drop ]
      [ ] if

    key-l keys nth
      [ g [ 1 - ] change-horiz-angle drop ]
      [ ] if
  ;