画蛇添足
Meaning
To ruin something good by adding unnecessary extras.
In a sentence
The design was fine until they 画蛇添足 and added three more fonts.
Usage note
Criticises over-engineering, not carelessness.
Where you see it in Brain Challenge
This idiom appears in the picture-idiom levels as a picture or number clue. When the clue shows numbers, the digits usually become the first characters of each half of the idiom — that is why so many chengyu start with 一, 三, 五, 七, 九 or 十.