Malwarebytes detects a problem with the play online link.
Viewing post in A Difficult Puzzle (2021) comments
The links are safe. Sometimes antivirus programs like to flag ADRIFT software (this game was made with ADRIFT) for a while until someone bothers to send in the file to a few of the antivirus companies, which will look into it and conclude that it was a "false positive" and stop flagging for a while. This happens because there are millions of viruses so antivirus software has to evaluate files by statistical methods which increases the risk of false positives, especially for niche software which are not used by many. As ADRIFT and games made with ADRIFT are available on the ADRIFT site (www.adrift.co - not .com) that could be the reason why Malwarebytes flag the site.