Ruby code brain teaser. Just copy paste to IRB and see for yourself. Question: why did the first example worked ? :)

magic.rb

# this Ruby method definiton will get defined successfuly
def  
  'magic !'
end

# but this Ruby method definiton will Fail with syntax error:  syntax error, unexpected keyword_end, expecting end-of-input
def   
  'magic !'
end

# Question on you: Why didn't the first example throw syntax error ? :) 
# Who will figure it out first ? :) 

Answer

1st Definition

The 1st definition has an Unicode character, specifically the character is U+2001.

It looks like an empty space.

Ruby allows creating methods using Unicode characters.

2nd Definition

The 2nd definition uses an empty space (ASCII 32, or 20 in hex).

An empty space is not a valid method name in Ruby.

Conclusion

Because the 1st definition uses an empty-looking character in the Unicode character set Ruby considers this a valid method name, but the 2nd definition uses an actual empty space, which is not valid.