Can't level up

My level 99 warrior on floor 154 has been fighting away and killing bad guys with a full green experience bar for ages. Is it impossible to reach a higher level? I’m still such a wimp . . .

Further reading on the Board has answered my own question, I think. Now I see no way to get tougher! Sigh.

Actually there is;) go to Hero -> Stats pane -> Adventure -> tap Challenges. A bunch of useful upgrades there:)