How can I make the keys randomly change after each keypress?

Hi guys,
I made a Tetris game and want to make the key for rotating the blocks change randomly after each keypress.
For example: first time using the “R” button in order to rotate the block but if I want to rotate the same block again, then I need to try another button…

void Update() {
        if (State != TetrimoState.Fixed && State != TetrimoState.Preview && State != TetrimoState.Spawning) {
            if (State != TetrimoState.Landed && Input.GetAxis("Vertical") < 0)

            if (Input.GetButtonDown("Horizontal"))

            // Set "up" as alternative button for Jump (Project => Input)
            if ((Input.GetButton("Jump")) && Time.time > NextSwap) {    
                if (this.CanRotate) {
                    NextSwap = Time.time + SwapCooldown;

            // Automatic falling down
            if (NextFall < 0) {
                NextFall = FallingCooldown;
            NextFall -= FallingSpeed * Time.deltaTime;

        if (State == TetrimoState.Preview) {
            transform.Rotate(0, 1f, 0, Space.World);

Store a string collection containing your keys.
Pick a random index within the collection’s length.
Use the string key at that index as your GetKeyDown argument.