1. Don't play computer games too much.

2. Don't play too many computer games.
3. Don't play too much computer games.
4. Don't play a lot of computer games.

5. Don't play smart phone games too often.
6. Don't play too many smart phone games.
7. Don't play too much smart phone games.
8. Don't play smart phone games too much.
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Which ones are incorrect? I think putting 'too much' before 'games' is not correct.

You are correct. The phrases "Don't play too much computer games" and "Don't play too much smart phone games" are grammatically incorrect. The correct forms would be:

1. Don't play computer games too much.
2. Don't play too many computer games.
3. Don't play a lot of computer games.
5. Don't play smart phone games too often.
6. Don't play too many smart phone games.
7. Don't play too much smart phone games.
8. Don't play smart phone games too much.

In English, the phrase "too much" is used before an uncountable noun, such as "unlimited", "air", or "water". However, both "computer games" and "smart phone games" are countable, so the correct phrasing requires the use of "too many" instead of "too much".

3 and 7 are incorrect.