Correctly writing a Zone File for a nameserver

I need to write a zone file for a new company domain. Let's say the company owns company.com and I need to write a zone file for 2 domains play1.playground.company.com and play2.playground.company.com . When defining the zone file Origin line, do I need to put in the whole FQDN play1.playground.company.com. or just play1.playground is enough? Will the following zone file work out?

$ORIGIN play1.playground.company.com.
$TTL 3600
@        IN    SOA      ns hostmaster ( 1614244859 7200 3600 1209600 3600 )
@        IN     NS    ns
@        IN     A    1.1.1.1
@        IN    MX    10 mail
ns       IN    A    10.0.0.2
mail     IN    A    10.0.0.1
www      IN    CNAME    play1.playground.company.com.
wwwtest  IN     CNAME    www 

$ORIGIN defines how unqualified names in your zone file should be completed.

You can use anything and even redefine $ORIGIN to change that substitution behavior for subsequent records in the same zone file.

But that will probably lead to a complete mess.

$ORIGIN should be fully qualified and end in . dot.

By convention $ORIGIN should be set to zone name that zone file belongs to and that is what Bind will do when it is not explicitly defined.

See also https://www.zytrax.com/books/dns/ch8/origin.html

Afterthought: I have also seen zonefiles where $ORIGIN is set to only the dot ..

That has the result that effectively no substitution takes place. That forces an zone administrator to always use FQDN's everywhere and means you can't use the @ shorthand but also prevents situations such as the example below where a missing full stop after what was intended as an FQDN results in a CNAME record pointing to play1.playground.company.com.play1.playground.company.com.

$ORIGIN play1.playground.company.com.
www      IN    CNAME    play1.playground.company.com 

I don't know if doing that makes a lot more sense but it does make both the record with and without the terminating . behave identical and as a sloppy zone administrator expects :

$ORIGIN .
www.play1.playground.company.com   IN  CNAME  play1.playground.company.com 
www.play1.playground.company.com.  IN  CNAME  play1.playground.company.com.