Rewind/replay redesign

[olofson]

While the rewind/replay system does eliminate the issues of players either running out of ships or accumulating ridiculous numbers of them, but the consequences of losing ships are still unclear. Players can just retry the difficult situations until they succeed, which gives the impressions of free infinite lives - but at the same time, this system potentially makes it possible to paint oneself into a corner out of which it is impossible to proceed in the campaign.

So, I came up with an idea:

• Rewinding has a certain cost. Rewind credits?
• When rewinding, you can choose to just replay, or at an extra cost (extra rewind credits?), deploy a new ship.
• When deploying a new ship, the old ship(s) will be replaying their respective timelines, as companion ships.
• A replay companion ship will either continue until destroyed, either the way it happened originally, or sooner, or if it somehow reaches the end of its timeline without being destroyed, it will teleport out, or otherwise vanish.
• Increase the difficulty, so that companion ships are more or less required in some parts of the campaign.
• The game is over when the player loses a ship, and can't afford to rewind or spawn a new ship.

These changes should make the game more challenging and interesting, while also providing an optional lifeline for difficult situations, and defining a clear game over condition.

See also #561.