Game of PIG - Sixes

PIG - Sixes - A game for two players, using two dice.

The winner is the first player to get $100$ or more points.
You both start with zero points and take turns to throw the dice
as many times as you like adding the total at each throw to your score.
Throwing one $6$ ends the turn and nothing is added to the score for that turn.
Throwing a double $6$ ends the turn and the total score goes back to zero.
Try playing against Piggy. Can you work out Piggy's strategy?

This text is usually replaced by the Flash movie.

Imagine we change the rules of the game. How would your strategy be affected?

A one-die version: Roll just one die. If you roll a six, your turn ends and your total reverts to what it was at the start of your turn.
A friendlier version: double sixes don't reset your total score to zero, but one or two sixes still ends your turn.
Game of PIG - Ones: If you roll a one, your turn ends, if you roll a double one, your total score is reset to zero. Sixes are safe.