How would I make the camera follow the players sprite horizontally instead of vertically?

Question

I have the following code and I've successfully made it to where the camera follows the player vertically, but I'm having some trouble making it follow the player horizontally. How would I do that? The code is in python as well.

   def update(self):
        # Game Loop - Update
        self.all_sprites.update()
        # check if player hits a platform - only if falling
        if self.player.vel.y > 0:
            hits = pg.sprite.spritecollide(self.player, self.platforms, False)
            if hits:
                self.player.pos.y = hits[0].rect.top
                self.player.vel.y = 0
        # if player reaches top 1/4 of screen
        if self.player.rect.top <= HEIGHT / 4:
            self.player.pos.y += abs(self.player.vel.y)
            for plat in self.platforms:
                plat.rect.y += abs(self.player.vel.y)
                if plat.rect.top >= HEIGHT:
                    plat.kill()