EnderCalc v1.0

function calculator()
term.clear()
term.setCursorPos(1,1)
term.setTextColor(colors.orange)
print("Please type your first number")
term.setTextColor(colors.white)
firstNum = read()
numOneIsValid = tonumber(firstNum)
	if type(numOneIsValid) == "number" then
		term.setTextColor(colors.orange)
		print("Please type your second number")
		term.setTextColor(colors.white)
		secondNum = read()
		numTwoIsValid = tonumber(secondNum)
		if type(numTwoIsValid) == "number" then
			term.clear()
			term.setCursorPos(1,1)
			term.setTextColor(colors.orange)
			print("What would you like to do with these numbers?")
			term.setCursorPos(1,3)
			term.setTextColor(colors.lime)
			print("{Add} {Subtract} {Multiply} {Divide}")
			local event, button, xPos, yPos = os.pullEvent("mouse_click")
			if button == 1 then
				if (xPos >=1 and xPos <=5 and yPos == 3) then
					term.clear()
					term.setCursorPos(1,1)
					local sum = (firstNum+secondNum)
					term.setTextColor(colors.lightBlue)
					print("The sum of your numbers is "..sum)
					term.setCursorPos(1,3)
					term.setTextColor(colors.lime)
					print("{Clear} {Exit}")
					local event, button, xPos, yPos = os.pullEvent("mouse_click")
					if button == 1 then
						if (xPos >=1 and xPos <=7 and yPos == 3) then
							calculator()
						elseif (xPos >=9 and xPos <=14 and yPos == 3) then
							term.clear()
							term.setCursorPos(1,1)
						else
							calculator()
						end
					else
						calculator()
					end
					sleep(3.5)
					startScreen()
				elseif (xPos >=7 and xPos <=16 and yPos == 3) then
					term.clear()
					term.setCursorPos(1,1)
					local diff = (firstNum-secondNum)
					term.setTextColor(colors.lightBlue)
					term.write("The difference of your numbers is "..diff)
					term.setCursorPos(1,3)
					term.setTextColor(colors.lime)
					print("{Clear} {Exit}")
					local event, button, xPos, yPos = os.pullEvent("mouse_click")
					if button == 1 then
						if (xPos >=1 and xPos <=7 and yPos == 3) then
							calculator()
						elseif (xPos >=9 and xPos <=14 and yPos == 3) then
							term.clear()
							term.setCursorPos(1,1)
						else
							calculator()
						end
					else
						calculator()
					end
				elseif (xPos >=18 and xPos <=27 and yPos == 3) then
					term.clear()
					term.setCursorPos(1,1)
					local product = (firstNum*secondNum)
					term.setTextColor(colors.lightBlue)
					term.write("The product of your two numbers is "..product)
					term.setCursorPos(1,3)
					term.setTextColor(colors.lime)
					print("{Clear} {Exit}")
					local event, button, xPos, yPos = os.pullEvent("mouse_click")
					if button == 1 then
						if (xPos >=1 and xPos <=7 and yPos == 3) then
							calculator()
						elseif (xPos >=9 and xPos <=14 and yPos == 3) then
							term.clear()
							term.setCursorPos(1,1)
						else
							calculator()
						end
					else
						calculator()
					end
				elseif (xPos >=29 and xPos <=36 and yPos == 3) then
					term.clear()
					term.setCursorPos(1,1)
					local quotient = (firstNum/secondNum)
					term.setTextColor(colors.lightBlue)
					term.write("The quotient of your two numbers is "..quotient)
					term.setCursorPos(1,3)
					term.setTextColor(colors.lime)
					print("{Clear} {Exit}")
					local event, button, xPos, yPos = os.pullEvent("mouse_click")
					if button == 1 then
						if (xPos >=1 and xPos <=7 and yPos == 3) then
							calculator()
						elseif (xPos >=9 and xPos <=14 and yPos == 3) then
							term.clear()
							term.setCursorPos(1,1)
						else
							calculator()
						end
					else
						calculator()
					end
				else
					term.clear()
					term.setCursorPos(1,1)
				end
			else
				term.clear()
				term.setCursorPos(1,1)
			end
		else
			term.clear()
			term.setCursorPos(1,1)
			term.setTextColor(colors.red)
			print("The Endermen are not amused!")
			sleep(3)
			calculator()
		end
	else
		term.clear()
		term.setCursorPos(1,1)
		term.setTextColor(colors.red)
		print("The Endermen are not amused!")
		sleep(3)
		calculator()
	end
end
calculator()