In a code language, 'keep it simple' is written as '426', 'bring the board games' is written as '5355', 'play by the rules' is written as '4235'. What is the code for the phrase 'puzzles are fun to play' in this language?

Let's count the number of letters in each word of the given phrases to check if that matches the code digit:
'keep' (4), 'it' (2), 'simple' (6) → Code: 426

'bring' (5), 'the' (3), 'board' (5), 'games' (5) → Code: 5355

'play' (4), 'by' (2), 'the' (3), 'rules' (5) → Code: 4235

The logic is that each digit represents the length of the corresponding word in the phrase.

Applying this logic to 'puzzles are fun to play':

'puzzles' → 7 letters

'are' → 3 letters

'fun' → 3 letters

'to' → 2 letters

'play' → 4 letters

Thus, the code is 73324.