Part 4: Evolving an API design

@font-face { font-family: 'livebook'; src:url('https://d19npu3b8zepp3.cloudfront.net/assets/fonts/livebook.eot?1.9.0'); src:url('https://d19npu3b8zepp3.cloudfront.net/assets/fonts/livebook.eot?1.9.0') format('embedded-opentype'), url('https://d19npu3b8zepp3.cloudfront.net/assets/fonts/livebook.woff?1.9.0') format('woff'), url('https://d19npu3b8zepp3.cloudfront.net/assets/fonts/livebook.ttf?1.9.0') format('truetype'), url('https://d19npu3b8zepp3.cloudfront.net/assets/fonts/livebook.svg?1.9.0') format('svg'); font-weight: normal; font-style: normal; }