It's a soft adjective, those end with -í in nominative regardless of gender. Check the tips and notes provided (click on the light bulb icon, web only at the moment).
How do I say "stranger things?"
"Zvláštnější" is the comparative form of 'zvláštní.'
when i looked at what strange meant at the bottom and it said cizi so i decided to type it down but it said i was wrong
What exactly is meant by the "voiced" and "unvoiced" consonant rule? What is "unvoiced" and what is "voiced"? Do I pronounce the "z" here, or only the "v" and "l"?
Have a look at the Tips and Notes for the Hello Skill: https://www.duolingo.com/skill/cs/Phrases/tips-and-notes.