"Geuss what number I mean" in Ruby

# Simple game "Guess what number I mean" in Ruby written by Mrowqa

class String
    def is_integer? # add our test
        self =~ /^[-+]?([0-9]*)?$/
    end
end

times = 0
Random::srand Integer(Time.now)
number = (Random::rand*100).to_i % 100 + 1 # 1..100
puts "Type number from 1 to 100 range: "

begin
    times+=1
    input = gets[0..-2]
    if not input.is_integer?
        puts "Wrong! This is *NOT* number. Try one more time:"
        times-=1
        next
    end
    no=Integer(input)

    case
        when no<1 || no>100
            puts "#{no} isn't from given range!"
            times-=1
        when no<number
            puts "#{no} is too small!"
        when no>number
            puts "#{no} is too big!"
    end
end while no!=number

puts "You guessed #{number} by #{times} time!"