input: 
  def encrypt(message: str, key: str) -> str:
      """ Encrypts a message using a key by shifting each character in the message by 
      the ASCII value of the first character of the key.
      >>> encrypt("Hello world!", "secret")
      'Tq$$$%t||$qd&'
      """
  
output:     encrypted_message = ""
      shift = ord(key[0])
      for char in message:
          if char.isalpha():
              if char.islower():
                  encrypted_char = chr((ord(char) - ord('a') + shift) % 26 + ord('a'))
              else:
                  encrypted_char = chr((ord(char) - ord('A') + shift) % 26 + ord('A'))
          elif char.isdigit():
              encrypted_char = chr((ord(char) - ord('0') + shift) % 10 + ord('0'))
          else:
              encrypted_char = chr((ord(char) + shift) % 128)
          encrypted_message += encrypted_char
      return encrypted_message