Learn Swedish: Han ryckte till när han såg spindeln. - He flinched when he saw the spider.

The verb rycka on its own normally means to pull, yank, or snatch. However, adding the aspectual particle till changes it into a phrasal verb describing a sudden, involuntary, or brief action. Together, ryckte till means to flinch, jerk, or startle, which perfectly describes his sudden physical reaction to seeing the spider.

Where does the spoken emphasis go in the phrase ryckte till?

Because this is a phrasal verb, the spoken stress always falls heavily on the particle till, not on the verb ryckte. Emphasizing the particle is a fundamental rule in Swedish pronunciation to show that the two words form a single unit of meaning.

Could I use other verbs with till in the exact same way to describe his reaction to the spider?

Yes! This is a very common pattern for physical reactions. Depending on what he did when he saw the spider, you could substitute the verb and say he hoppade till (gave a sudden jump), skrek till (let out a brief yelp), or ryste till (gave a sudden shiver). The particle till always adds that sense of a quick, momentary burst.

Could I use då instead of när to mean 'when' in this sentence?