Adding points to players in RPS Game - ruby

Question

I'm creating a Rock Paper Scissors game. There are no errors but it doesn't work how I would like it to.
Instead of adding the scores to the player it just ends when the player rolls for their choice by pressing either "R" or "E"
I don't understand what's happening here could someone please explain to me why it's not doing the adding?
def welcome
puts "Welcome to Rock, Paper, Scissors. To begin press 'S'.
To learn how to play press 'I'. To quit the game press 'Q'"
input = gets.chomp
if input =~ /s/i
start_game
elsif input =~ /i/i
instructions
else
exit
end
end
def start_game
start_points_P1 = 0
start_points_P2 = 0
choice = ['Rock', 'Paper', 'Scissors']
choicep2 = ['Rock', 'Paper', 'Scissors']
puts "Press 'R' to roll for Player 1"
input = gets.chomp!
puts "Press 'E' to roll for Player 2"
input = gets.chomp!
if choice.sample == choicep2.sample
puts "Draw!"
start_game
elsif choice.sample == 'Paper' && choicep2.sample == 'Scissors'
puts "Player 2 has won! You have gained 10 points! Score: Player 1: #{start_points_p1} Player 2: #{start_points_p2 += 10}"
elsif choice.sample == 'Scissors' && choicep2.sample == 'Rock'
puts "Player 2 has won! You have gained 10 points! Score: Player 1: #{start_points_p1} Player 2: #{start_points_p2 += 10}"
elsif choice.sample == 'Rock' && choicep2.sample == 'Paper'
puts "Player 2 has won! You have gained 10 points! Score: Player 1: #{start_points_p1} Player 2: #{start_points_p2 += 10}"
elsif choicep2.sample == 'Paper' && choice.sample == 'Scissors'
puts "Player 1 has won! You have gained 10 points! Score: Player 1: #{start_points_p1 += 10} Player 2: #{start_points_p2}"
elsif choicep2.sample == 'Scissors' && choice.sample == 'Rock'
puts "Player 1 has won! You have gained 10 points! Score: Player 1: #{start_points_p1 += 10} Player 2: #{start_points_p2}"
elsif choicep2.sample == 'Rock' && choice.sample == 'Paper'
puts "Player 1 has won! You have gained 10 points! Score: Player 1: #{start_points_p1 += 10} Player 2: #{start_points_p2}"
end
end

Answer 1

Every time you call sample on choicep2 or choice, a random value will be selected from the array you call it on. You should do something like player_choice = choice.sample, computer_choice = choicep2.sample (or computer_choice = choice.sample will work just as well) then make the comparison between player_choice and computer_choice.

Answer 2

Probably the biggest problem in the code in terms of the functionality you want is the repeated use of choice.sample and choicep2.sample. Every time that is called, it returns a new random selection from each array.
That means for each test like this:
elsif choice.sample == 'Paper' && choicep2.sample == 'Scissors'
there is an independent 1 in 9 chance of it being true and you seeing the result. That means it is possible to fail all the tests, because for each condition the "players" are going again, and you only check one possible exact outcome. This is not like the real version of this game at all, where the players make a single choice each and then you test it.
To fix this in a way which matches how this game is usually played, you should store each player's choice in a new variable, and compare those values. E.g. before your first test, do something like
p1_plays = choice.sample
p2_plays = choice.sample
(Note how you can re-use the list of choices, as it does not change, at least in this variant)
Your conditionals can then refer to those variables like this:
elsif p1_plays == 'Paper' && p2_plays == 'Scissors'
As an aside, it may be a nice addition to your code to show what each player played. If you do that as one of the first things, then it will help you verify correct logic in the rest of the code.