How to Mark Long Vowels

Vowels can be long or short. They can have normal or high tone. They can be nasal or oral. So, how do you mark a long vowel? You do not have room for a make-ron, so they simply write the vowels twice. That's kind of standard, isn't it? I think in some languages it's standard. It's fairly common, but not that common. Two tone and three tone systems are easy to deal with. And they're common. Contour tone systems will mess with your head. But don't just use Unicode unless you freaking need it. If you need enema or epsilon or the backwards C thing, or if