head to head
Styx: Shards of Darkness asks more than Portal, and the gap is variance.

Optimization · Pure Optimization
The portal-gun puzzle game whose solutions are everything.

Optimization · Pure Optimization
Managing clone resources and mapping patrol circuits to chain ghost kills through vertical levels.
Portal leans Optimization (Pure Optimization); Styx: Shards of Darkness leans Optimization (Pure Optimization).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Portal
Portal placement timing modest.
Styx: Shards of Darkness
Climbing and kill-window timing are modest but present demands
Styx: Shards of Darkness leans a little harder on reads, though the gap is small.
Portal
No adversary modeling player.
Styx: Shards of Darkness
Dark Elves and Dwarves use scripted patrol trees throughout
Styx: Shards of Darkness leans clearly harder on variance.
Portal
Deterministic chambers; no randomness.
Styx: Shards of Darkness
Level geometry is consistent; knowledge transfers cleanly between attempts
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Portal
Pure puzzle-solving optimization.
Styx: Shards of Darkness
Clone economy, rope optimisation, and route planning are the lead skill
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.