how is it? Is it difficult?
I mean I'm doing quite well in it; ranking 1st / borderline 2nd rn.
If you understand the main concepts of licenses, software approaches and how to write decent pseudocode and algorithms, Year 12 shouldn't be too hard. Most of the HSC content is very similar to Prelims; I feel like we only started learning new stuff (e.g., Sorts and Searches, Option Topic: Binary) towards the second half of the year. You should also (depending on your school) have a large practical programming assignment, and the trick with that is to not go too overboard and keep it simple to hit the key rubric areas.
Imo, SDD isn't too bad imo since most of the content (e.g., licenses, approaches, copyright stuff) is all common sense. The hard stuff is the algorithm writing under time pressure, metalanguages, your option topic, and more complex stuff like understanding the CPU and Fetch-Execute cycle.
If you stay on top of your weekly work and put in some effort, there isn't any reason not to keep a high-ish mark without going crazy, plus you'd keep and secure your high rank. Try make keeping your rank an incentive: that'll help push you to stay on track. Personally I'm interested in the theory that we learn, and it does actually help to go ahead a bit and watch a few yt videos to get that extra bit of understanding over your peers.
As a sidenote, SDD actually scales somewhat decently (on par with other subjects like Bio), so if that is something you're worried about - don't be.
You got this, whatever decision you make will be a good one - you seem on top of every other subject by your marks.
