Rock / Paper / Scissors [C]

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

int playerChoose()
{
    char player_string;
    int player_choice = 0;

    printf("\nMake your choice using one of the letters: 'R' / 'P' / 'S':\n\n");
    scanf(" %c", &player_string);
    player_string = (char)toupper(player_string);

    if(player_string == 'R') {
        printf("\nYou chose rock.\n");
        player_choice = 1;
    } else if(player_string == 'P') {
        printf("\nYou chose paper.\n");
        player_choice = 2;
    } else if(player_string == 'S') {
        printf("\nYou chose scissors.\n");
        player_choice = 3;
    } else {
        playerChoose();
    }

    return player_choice;
}

int computerChoose()
{
    srand(time(NULL));
    int computerChoice = 1 + rand() % 3; /* Return a random number between 1 and 3 */

    if(computerChoice == 1) {
        printf("\nThe computer chose rock.\n");
    } else if(computerChoice == 2) {
        printf("\nThe computer chose paper.\n");
    } else if(computerChoice == 3) {
        printf("\nThe computer chose scissors.\n");
    }

    return computerChoice;
}

int compareChoices(int playerChoice, int computerChoice)
{
    if(playerChoice == 1) { /* User chooses rock */
        if(computerChoice == 1) { /* Computer chooses rock */
            printf("\nIt's a tie!\n");
        } else if(computerChoice == 2) { /* Computer chooses paper */
            printf("\nThe computer wins.\n");
        } else if(computerChoice == 3) { /* Computer chooses scissors */
            printf("\nYou win!\n");
        }
    } else if(playerChoice == 2) { /* Player chooses paper */
        if(computerChoice == 1) { /* Computer chooses rock */
            printf("\nYou win!\n");
        } else if(computerChoice == 2) { /* Computer chooses paper */
            printf("\nIt's a tie.\n");
        } else if(computerChoice == 3) { /* Computer chooses scissors */
            printf("\nThe computer wins.\n");
        }
    } else if(playerChoice == 3) { /* Player chooses scissors */
        if(computerChoice == 1) { /* Computer chooses rock */
            printf("\nThe computer wins.\n");
        } else if(computerChoice == 2) { /* Computer chooses paper */
            printf("\nYou win!\n");
        } else if(computerChoice == 3) { /* Computer chooses scissors */
            printf("\nIt's a tie.\n");
        }
    }
}

void playAgain()
{
    char play_again;
    printf("\nDo you want to play again? 'Y' / 'N'\n\n");
    scanf(" %c", &play_again);
    play_again = (char)toupper(play_again);

    if(play_again == 'Y') {
        playGame();
    } else if(play_again == 'N') {
        printf("\nThank you for playing.\n");
    } else {
        playAgain();
    }
}

void playGame()
{
    int playerChoice = playerChoose();
    int computerChoice = computerChoose();
    compareChoices(playerChoice, computerChoice);
    playAgain();
}

int main()
{
    playGame();
    return 0;
}