Saving
Learning paths through this topic
How to Make Save Games That Keep the Story
A save must store what happened in the story, not only where the player stands. Model saving and loading as steps, and a checker finds what gets lost.
Checkpoints
Checkpoints keep a death from costing the whole level. The player risks only the stretch since the last marker, so a hard part can be tried again and again without walking the same easy part each time.
Autosave
Autosave means a crash, a dead battery or a closed window costs the player a minute of play and not an evening. The player never has to think about saving, and the game never freezes at a bad moment to do it.
The autosave kicks in during a boss fight and the save can never be won
Saving by timer is simple, but it will sooner or later save at the worst possible moment, such as when the player is nearly dead. Here is a set of rules for when the game may save by itself, and when it must wait.
Players set their phone clock forward to collect a week of offline rewards
Rewards for the time a player was away only make sense if nobody can lie about how long that was. Here is whose clock to trust, how to stop long absences from being worth too much, and what to do when the numbers make no sense.
Griefing is noticed days later and every backup is already overwritten
Keeping only the last few backups protects against a crash but not against the thing people notice a week too late. Here is a thinning rule that keeps many recent copies and a few old ones, with a count that stays small however long the server runs.
After a crash a player's gold no longer matches what they earned and spent
Keeping only the current amount means that one lost write leaves a number nobody can explain, and one repeated write gives free money. Here is a simple record of every change that can check the total, refuse a bad spend and repair itself.
A slow phone uploads an old run last and wipes out the player's best score
Scores can reach the server in a different order than they were earned, and some arrive with numbers nobody could have reached. Here is how to keep the best and the latest result apart, and how to throw out the impossible ones without punishing honest players.
A boss scaled for four players becomes broken when two of them leave
Enemies that grow tougher with more players need to keep their wounds in a form that survives the party changing, a save and a reload. Otherwise the boss heals, dies at once or ends up with more health than its maximum.
A friend brings an overpowered character from their own world into yours
Characters that travel between worlds can carry things your world has never heard of, or numbers far past what it allows. Here is how to let them in without ruining your game and without destroying anything that belongs to the visitor.
Two builders place different blocks on the same spot and the world keeps neither properly
In a shared world many people change tiny pieces at once, and the save must hold only what changed. Here is how each spot carries its own change counter, how a late builder is told no, and the small trap that appears when something is removed.
An action aimed at a part of the world nobody has loaded gets lost
A letter dropped into a faraway barrel, a spell cast on a distant field or a delivery to a base nobody is near all target something that is asleep. Here is how to queue the change, apply it once on waking and survive a crash between the two.