final-key_pressed-function.js

function key_pressed(key)
      {
        ... // arrow up block

        if (key.key == "ArrowLeft")
        {
            console.log("left");
            player_x -= player_move_increment // reduce player_move_increment, which moves player left
        }

        if (key.key == "ArrowRight")
        {
            console.log("right");
            player_x += player_move_increment // increase player_move_increment, which moves player right
        }
      }