What Are Game Trailer Spoilers?
Can a game trailer spoil a game and if so, how?
Movie trailers have long held a reputation for showing too much of the movie, but why is it games don't share the reputation? I think a large part of it is that while many games do have stories, there are a huge percentage which have little to no story. More importantly, games are generally about the experience of playing the game, not seeing the game. As players, experiencing a moment in a game is a very personal experience even if it's a game which plays out pretty much the exact same way for every single player.
To make an extreme comparison, I'm guessing mountain climbers who see photographs or videos of the top of Mount Everest aren't any less interested in going, they're likely MORE interested because they know the experience of doing it themselves is a large part of the appeal; the appeal isn't knowing what's there upon arrival.
If the experience of a game is playing it, that means it largely cannot be spoiled because watching footage on a YouTube video or Twitch stream will never compare to pressing the buttons with your own hands which caused something on screen to change.
That said, there are things in games which can be considered spoilers, including:
Story details
Puzzle solutions
Secrets
Knowing this dragon exists in Dark Souls is one thing, but discovering it for yourself and then fighting it is another thing entirely.
Story details
Story spoilers for game trailers are no different than for movies. If the trailer asks a big question like "Will they survive and get off the island?" then yes, that is 100% a spoiler and should be avoided. Big questions should generally be presented in a trailer and left unresolved, whereas scene setting expositional questions are good things to answer.
Questions which are ok to answer:
Who is this character?
What is happening in the world?
Who is the antagonist?
How are they going to try to succeed/win?
Questions which should NOT be answered:
Do they succeed?
Does this person live to the end?
Is their relationship successful?
What is REALLY happening in this mystery?
I feel like people generally have a decent instinct for whether or not something is a story detail spoiler, but a good way to audit a trailer is to go through the story details, list what questions the trailer presents, and the answers it provides (if any). If the answers presented are things you want the player to experience for themselves, you might want to take them out.
The trailers for The Last of Us Part 2 avoided showing certain details to keep major story AND gameplay affecting features secret.
Puzzle Solutions
Some games have very clear and visual answers to the puzzles they present to the player, and in those cases you're probably going to want to avoid showing them. For example, a trailer for Myst shouldn't show the correct combination to the Mechanical Age gear because that removes all the necessity of discovering that solution. Even someone who sees that and has a desire to use their own powers of deduction to solve the puzzle will likely feel cheated.
This doesn't mean puzzle games can't show things getting solved. To understand a game has puzzles in it, it's usually necessary to show the player interacting with a puzzle and some sort of results of solving the puzzle. For example, lasers being activated in The Witness or Manifold Garden. Puzzle sequences in point and click adventure games are also fairly safe to show sections of too! In all of these cases, there's really only enough time in a trailer to show part of a solution and the end result, thus keeping the solution of the puzzle safe.
Again, if there's something in the game like a door combination which can be immediately implemented to skip over large sections of the game, that is of course going to be a spoiler. Even if the game randomizes a combination to make it different each time, the person watching might still feel like they're being spoiled, so it's still worth avoiding.
Showing this clock and the valves turning would be ok in a trailer, but showing the correct time to set it to would definitely not.
Secrets
There are a lot of games where a large part of the experience is discovering new things. For example, the core experience of the game Frog Fractions is about surprise and discovery. The trailer for the new edition on Steam avoids the parts of the game which would ruin the surprise of the game. If the trailer showed more, a core part of the experience would be lost.
For Spelunky 2, we had to be very careful about what we did and didn't show, all while making trailers which showed just a little bit more than the previous one. The parts we felt safer to show were things like new enemy types with unique behaviors, and some fundamental game changing differences like flowing liquids and branching pathways.
Things we avoided were solutions to the "puzzle" sequences of the game because we knew Spelunky players and the community would enjoy playing and sharing notes and theories. I even went so far as to swap some game textures in the first gameplay trailer in order to obfuscate a solution even though I showed the effectof solving one of the steps. There are also some parts of the game which we left out because we knew they would answer some lingering questions being discussed intently by the community.
It would've been great to let all potential Spelunky 2 players discovery every pixel of the game on their own, but it would've been much more difficult to build hype.
Game secrets are much trickier type of spoiler to balance because they can be a key selling point of a game, and withholding their existence might result in a weaker and less enticing trailer. In some cases I think it's ok to spoil some secrets if it's something like a hidden coin in a Super Mario game, especially if there isn't enough context for the player to fully know the location. In that situation, showing the secret hopefully expands the scope of the game in the eye of a player who might otherwise not test the boundaries of the game space.
I first got thinking about this topic of game trailer spoilers after seeing this tweet from @StarlightSkyes:
I don't know the games she's referring to, but I'm guessing the developers she's talking about believe the ideal experience for a player of their game is to go in as cold as humanly possible so every little moment is a magical discovery or surprise.
The problem is, game trailers cannot create mystery using the same techniques and shots as movies trailers because we need to know so much more about a game in order to be at all interested. We don't need to be taught how to watch a movie, that's why presenting some cool shots and vague dialogue can be enough to entice us in a movie trailer. For a game trailer, a bunch of cool environments are meaningless, and seeing unique characters without knowing what they do or how they move leaves us with the wrong sorts of unanswered questions.
The other key difference between movies and games is most people do not finish games they start playing. Apparently, 30-40% of players finishing a game is cause for celebration amongst developers, whereas my unscientific googling for people not finishing movies mostly yielded articles about people too scared to watch all of a horror film. This means weakening the marketing materials for the sake of protecting secrets might be all for naught if even the players of the game never see the things you hid.
Every DLC trailer for Dead Cells showed the new boss battle. Yes, it would be cool to discover on your own, but it made the trailers much more exciting and enticing!
One other thing to remember is trailers are more for the customers than for the developers. You are not helping the customer when you withhold information they need to properly evaluate the game and decide whether or not to spend their money on it. Something which happens at the end of a movie is a spoiler because anyone willing to sit through the film is guaranteed to see that moment. Something which happens at the end of a game is not something you can guarantee a player of the game will see either because of the skill ceiling or just a willingness to persevere to the end.
Under the best of conditions, interesting mid to late game content could be seen as a challenge to the player. Ideally, they think: "Wow, I can't wait to get to that part of the game!" If the goal is to keep the experience as fresh as possible without showing a lot of variety in a game trailer, I think at best the way to do it is to make the trailer as short as possible. But frankly, I think if the goal is to get people to play the game, showing some degree of variety and new exciting stuff is key.
It ultimately comes down to whether or not: you're answering questions the audience doesn't want answered. Knowing your audience and community's wants and needs are key to knowing if/when you've gone too far with spoilers. This is one of many reasons I was so happy to be making the trailers for Spelunky 2. Even if I'm not deeply involved in the community, my hundreds (thousands?) of hours playing the game and talking about it with friends made it much easier to look at something in the game and understand whether or not it would feel like it would spoil a fun discovery in the game, or if it would whet their appetites.