The game is designed so that "there's just a great deal of freedom" for the player, says Blow. Players can choose to doggedly solve clusters of puzzles, walk around sampling the island in any order they choose, or the "whole spectrum in between that," says Blow. It's the same kind of freedom to pick and choose which players had in Braid, but in full 3D.
Says Blow, "It's just interesting to give players that choice. There's narrative stuff happening, but I don't know what order the player is going to listen to it in. Constructing something made for that level of freedom is actually a little bit challenging."
Most 3D games offer a "a tightly-controlled linear experience", says Blow, giving him few cues on how to design something that can be played in any order. "And so you have to abandon the influence of so many games in order to get back to a head space where it's like, 'No, let's just do something that makes sense in this kind of structure,'" he says.
While just about everybody has compared the game to Myst based on how it looks, there's a crucial difference between The Witness and the adventure games of old.
"With adventure games, [there's] this idea that you have a key/door puzzle. 'I need to go find the key' -- and maybe there's a puzzle to even get the key -- 'and then I can open the door.' So this game has that all over the place, but the key is just in your head," says Blow.
Once players learn the way a puzzle works, and become proficient at solving it, they can simply move on to the next. Most puzzles are freely accessible at any time, and few are gated by anything but the player's own knowledge and skill. Aside from a few locked buildings, the vast majority of the island is accessible from the get-go.
He's also been experimenting with how clear to make things: whether each puzzle should lead the player on to another. The landscape of The Witness is crisscrossed with power cables that you can trace to new destinations.
"My thinking has evolved over time," says Blow. "Originally the power cables were part of that extreme clarity. Like, you solve the panel, and there's not a question of where to go next. But what I've found as I work on the game a little more is that I like if there's some variability. So early in the game we can have a lot of clarity, but then later on maybe some are harder to follow."
Pacing can also be a challenge for him. Early versions of the game "felt grindy" for players, as they solved puzzle after puzzle without break, says Blow. To that end, he's changing the island's structure so that the areas offer clusters of different sorts of things -- exploration, puzzle-solving, and story. "So it's like a little bit of like a scavenger hunt or something, almost, and that's been kind of nice. I like it, actually."
However, he is aware that the "paradox of choice" can set in: "people just get grumpy" when they have no sense of what they should be doing. "But now we've got a lot more trees that sort of cloak areas and stuff, and there's more of a feeling of revealing new parts of the island as you walk around."
What's important to Blow is that players approach the game with a sense of curiosity. "The design of this game makes a great deal of assumption that you actually are going to proceed forward with that kind of game thinking... Because the game doesn't push you into anything."
While the island is interesting to explore, the panel puzzles form the core of The Witness. Generally, these puzzles look simple, but can be surprisingly challenging to solve. "Another fun thing to explore was [how] these things can get kind of hard sometimes, even just with this small number of elements," says Blow.
The early puzzles teach you how they work, and later ones add new elements, such as colored dots that must be separated by the line you trace. "And then on top of that, there's just a layer of ramping difficulty across all these puzzles," says Blow.
As a designer, Blow has become interested in the tension between logic and intuition in puzzle design. One puzzle, in which the player must observe apple trees in the environment, whose branches echo the maze on the panel, is "completely illogical," says Blow, but "nobody has ever, ever failed to get the apple trees, all three of them." That part of the game is "not about logic, it's just about intuition."
Blow's thinking about the game takes the sort of intuitive leaps he hopes the player will. When the player solves a puzzle, "there's that a-ha thing that happens," says Blow. But, he says, "what interests me is not that rush of like, 'Oh, I understand this now,' but it's the thing that the player understands now.
"I guess because of that, my design thought is focused on what's going through the player's head right now... now... now... all the time. And so, that's just kind of the way that I see stuff. And so I'll think about a puzzle. And I'll think about it like, 'Well, okay, when the player sees this -- before they understand what it means -- what are they going to be thinking?'"
Though Blow likes to think he can understand the player's frame of mind, he knows it's "impossible". "I have some ideal player, who I don't know who that is exactly, but it's somebody who likes the kind of games that I like, or something. And so I just think about, 'What would that ideal player do in this situation?' And that guides some decisions sometimes. I don't know. It's really an off-the-cuff kind of process," Blow admits.
He's not worried, however, by getting off-track as the game expands in scope and starts to grow beyond its initial design space. "This game has something in common with Braid, where the design process was first. I go find some interesting things, and then I try to curate them, and illustrate them in the form of these puzzles.
"But the fact that I found those interesting things -- those are there," says Blow, referring to different real-world phenomena, such as the fact that colored glass affects what you see through it. Colored dots shift tone when seen through yellow or blue windows, and an impossible puzzle can suddenly be solved.
"Because that stuff is at the core of the game. That stuff is not bullshit. That's the universe we live in, right? And because of that it's just kind of interesting. As a game designer, sometimes I can do a better job of building a puzzle to illustrate that, and sometimes I can do a worse job. I could build a bad puzzle. Hopefully I don't. Hopefully I catch it, and make it better. But let's suppose I still build bad puzzles. The game is still good, at some level, because it's got that stuff at the core," says Blow.
"This is not about me trying to impress people with my game design. I'm trying to make a really interesting and nice game design, but it's for something. It's utilitarian. It's trying to get at these ideas that are in there."