What makes a good game tutorial?
Teaching through play rather than through text, and introducing exactly one idea at a time in a situation where using it is the obvious thing to do. The best tutorials are the ones players do not notice.
The principles that hold up:
Teach by designing the problem, not by explaining the answer. A room whose only exit is a high ledge teaches jumping without a prompt. The classic example is an opening screen constructed so that moving right, meeting an obstacle, and discovering the jump all happen without a word of instruction.
One mechanic at a time, in a safe space, then combined with something learnt earlier.
Immediate application. Anything taught and not used within seconds is forgotten — which is why front-loaded tutorials that explain the entire control scheme before anything happens fail so reliably.
Let the player fail cheaply. Understanding comes from a mistake with a small cost, not from being told.
Distribute teaching across hours, introducing systems when they become relevant rather than at the start.
Respect what the player already knows. Conventions within a genre do not need teaching; departures from them do.
What goes wrong:
Text walls and modal popups, which interrupt and are skipped.
Locking controls during explanation, which players experience as being talked at.
Teaching something used once, an hour before it is needed.
Unskippable tutorials for returning players, which are actively hostile on a second playthrough.
The tutorial being unrepresentative, so the actual game feels nothing like the opening.
Hiding the genuinely non-obvious while exhaustively explaining the obvious — most games teach the jump button and never explain the systems people actually struggle with.
How it is validated. Through playtesting with people who have never seen the game, watching where they hesitate, and measuring drop-off rates at each step. This is a different activity from QA — QA asks whether it works; playtesting asks whether it is understood.
Tooltips and a searchable glossary are the correct home for reference material, letting the tutorial stay about doing.