Using an if function in controller

I'm trying to make an application to store played FIFA games.

Now I'm already able to make accounts, store games, etc. But when I'm storing a game into the DB, I would also like to store the winner and loser of the game in a way that I can use the count function later to count how many wins or losses a user has.

Controller:

class GamesController < ApplicationController
    before_action :authenticate_user!, exept: [:index, :show]

    def index
        @games = Game.all
    end

    def new
        @game = current_user.games.build
        @user_options = User.all.map{|u| [ u.user_name, u.id ] }
    end

    def create
        @user_options = User.all.map{|u| [ u.user_name, u.id ] }

        @game = Game.new(game_params)
        @game.home_team_user_id = current_user.id

        if @game.home_score > @game.away_score
            @game.winner_id = @game.home_team_user_id
            @game.loser_id = @game.away_team_user_id     
        else if @game.home_score < @game.away_score   
            @game.winner_id = @game.away_team_user_id
            @game.loser_id = @game.home_team_user_id  
        else
        end

        if @game.save
            redirect_to games_path, :notice => "Successfully added game!"
        else
            render 'index'
        end
    end

    def show
        @games = Game.all
    end

    def destroy
        @game = Game.find(params[:id])
        @game.destroy
        redirect_to games_path
    end

    private
    def find_game
        @game = Game.find(params[:id])    
    end

    def game_params
        params.require(:game).permit(:home_team_user_name, :home_score, :away_team_user_name, :away_score, :home_team_user_id, :away_team_user_id, :winner_id, :loser_id)
    end
end
end

View:

<div class="col-md-12" style="text-align:center">
  <div class="panel panel-default" style="margin-right:10px">
    <div class="panel-heading">
      <h3 class="panel-title">Submit New Match</h3>
    </div>
    <div class="panel-body">
      <%= simple_form_for(@game) do |f| %>
      <%= f.text_field :home_score, :placeholder => "Your score" %>
      <%= f.text_field :away_score, :placeholder => "Your Opponents score" %> <br><br>
      <p>Opponent:</p>
      <%= f.select(:away_team_user_id, @user_options) %>
      <br> <br> <%= f.submit "Submit Match", class: "btn-submit" %>
      <% end %>
    </div>
</div>

Is this the correct way to make this calculation? Or do you have other suggestions?

If this is the correct way, then why do I get this error when I try to submit the form:

undefined local variable or method `game_params' for

As you can see in the controller, the game_params is not missing. I've added an end at the end though, because this gave an error to load the form.