There are bugs in generated pot file.

How to reproduce: msginit --locale=zh_CN --input=.i18n/Game.pot --output=.i18n/Game-zh_CN.po .

Line 54 in 18e0aec

    
           "Each level in this game involves proving a mathematical theorem (the "Goal").\n"

here no \ berfore " in "Goal".

Line 76 in 18e0aec

"under the goal and hit "Execute"."

The same.

Line 102 in 18e0aec

    
           "* `rw [← h]` (changes `Y`s to `X`s; get the back arrow by typing `\left ` or `\l`.)\n"

Should use \\ in \left and \l.

Line 205 in 18e0aec

""\n"

should be \"\n.

Line 240 in 18e0aec

"Before we can use `rfl`, we have to "substitute in for $y$".\n"

The same, add \ before ".

Ill opened an issue over there and will fix this next week. Should be in the NNG when it updates to the next Lean toolchain