Tk Есть ли ошибки в коде?

#encoding: UTF-8
 
require 'tk'
 
app = TkRoot.new do
  title 'Калькулятор индекса массы тела'
end
 
label_of_weight = TkLabel.new(app) do
  text 'Вес'
end
label_of_weight.grid :column => 1, :row => 1
 
spinbox_of_weight = TkSpinbox.new(app) do
  to 727
  from 1
end
spinbox_of_weight.grid :column => 2, :row => 1
 
label_of_kg = TkLabel.new(app) do
  text 'кг'
end
label_of_kg.grid :column => 3, :row => 1
 
label_of_height = TkLabel.new(app) do
  text 'Рост'
end
label_of_height.grid :column => 1, :row => 2
 
spinbox_of_height = TkSpinbox.new(app) do
  to 251
  from 1
end
spinbox_of_height.grid :column => 2, :row => 2
 
label_of_cm = TkLabel.new(app) do
  text 'см'
end
label_of_cm.grid :column => 3, :row => 2
 
button_of_calculate = TkButton.new(app) do
  text 'Рассчитать'
end
button_of_calculate.grid :column => 2, :row => 3
 
label_of_bmi = TkLabel.new(app) do
  text 'ИМТ'
end
label_of_bmi.grid :column => 1, :row => 4
 
entry_of_bmi = TkEntry.new(app) do
  state 'readonly'
end
entry_of_bmi.grid :column => 2, :row => 4
 
label_of_state = TkLabel.new(app) do
  text 'Состояние'
end
label_of_state.grid :column => 1, :row => 5
 
entry_of_state = TkEntry.new(app) do
  state 'readonly'
end
entry_of_state.grid :column => 2, :row => 5
 
button_of_calculate.bind('ButtonRelease-1') do
end
 
Tk.mainloop

ruby твой-файл.rb