This simple self-contained puzzle is a lock/gate built into a Google sheet. This "firewall" requires that the players input a magic square.
This puzzle is similar to Norton Mini - A Simple Google Sheet Puzzle. It is a little google sheet page that separates the players from the digital asset they are after. If they can figure out how to hack past it, then they can proceed along a revealed hyperlink to the next thing.
In this time of shelter-in-place, I have found myself using digital tools for social interaction. The online Google products, namely Docs, Sheets, and Slides, turn out to be particularly useful for designing little puzzles that players can engage with collaboratively.

The "Magick Firewall" presents itself as a single sheet with a prominent "ACCESS DENIED" cell. Players can see a bunch of red FALSE cells.
The solution requires that the players input a magic square. That is, a 5x5 square of digits using every digit from 1:25 exactly once, with every row, column, and diagonal summing to the same value.

Different red cells check for different conditions. They light up green when their condition is met.
Players can use this information to figure out what to do.
Once a correct magic square is written in, the bottom cell turns to "SUCCESS!", which can have a hyperlink on it to move to the next digital asset (another google sheet, doc, or slide deck? Some other URL? Who knows?!)

Introducing Magic Squares
Basically no-one can derive a magic square from scratch without help. That being said, if players are doing this online, they may be allowed to search for one. Other players may be programming savvy and could solve for one that way. Alternatively, a partially completed magic square could be hidden elsewhere in the play session, and the players could use that as a starting point.
Under The Hood
There really isn't much under the hood. Most of the logic is on the main sheet.
There is a hidden sheet that gets referenced for the solution cell. If the magic square is correct, then the link below the mini points to the SUCCESS! cell (which has a hyperlink) instead of the original ACCESS DENIED cell. You can change the puzzle, change the text, change the hyperlink, etc.
Players can of course get too clever using Google sheet tricks to try to back out what is in this hidden sheet. As a DM it is up to you to what extent you want to lay down ground laws or let them "cheat".
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- Norton Mini - A Simple Google Sheet Puzzle by Mageek Bound
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- Norton Mini - A Simple Google Sheet Puzzle Alongside Mageek linked by Mageek
These are great little side challenges and the fact that you give us everything we need is fantastic. Great idea!!!