Come summer, beauty is a tricky field to navigate. Mascaras become waterproof but are a nightmare to take off; hair gets wilder, thanks to the humidity; nail polish lasts about 24 hours before peeling away. One of the most frustrating aspects, though, is applying your makeup in the morning only for it to slide off by lunchtime. And that's just in the office – on a summer night in Porto, you know that foundation isn't going to last.