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A few things you need to know about CSS      @sheiko

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What the heck is CSS anyway?

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CSS is a declarative language used for describing look & feel of a document

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MACHINE-READABLE DOCUMENT Data XML, HTML, SVG, …

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adding some style Data Look & Feel ? XML, HTML, SVG, … CSS

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XML, HTML, SVG, … HUMAN-READABLE DOCUMENT Data CSS Look & Feel

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The basics

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Hello World

  h1 { color: yellow; font-size: 2.4em; } HTML CSS OUTPUT Hello World

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Hello World

  .hello { color: yellow; font-size: 2.4em; } HTML CSS OUTPUT Hello World

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h1 { color: black; font-size: 2.4em; } rule CSS

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h1 { color: black; font-size: 2.4em; } selector declaration CSS

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h1 { color: black; font-size: 2.4em; } property value CSS

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Selectors

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    Hello   

h1 em { color: yellow; } h1 a em { color: yellow; } h1 a > em { color: yellow; } HTML CSS OUTPUT Hello World

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Inheritance

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  Hello 

  body { color: white; } h1 { color: yellow; } HTML CSS OUTPUT

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  Hello 

  body { color: white; } h1 { color: yellow; } HTML CSS OUTPUT Hello World

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Specificity

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    Hello World   

.parent .child { color: white; } h1 em { color: yellow; } HTML CSS OUTPUT

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    Hello World   

.parent .child { color: white; } h1 em { color: yellow; } HTML CSS OUTPUT Hello World

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What else you can do with CSS

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Turning elements into graphical shapes

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div{ width: 200px; height: 200px; background: yellow;  } HTML CSS OUTPUT

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div{ width: 200px; height: 200px; background: yellow; border-radius: 20px; } HTML CSS OUTPUT

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div{ width: 200px; height: 200px; background: yellow; border-radius: 50%; } HTML CSS OUTPUT

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div{ width: 0; height: 0; border-width: 200px; border-style: solid; border-color: transparent; border-top-color: yellow; } HTML CSS OUTPUT

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div{ width: 0; height: 0; border-width: 200px; border-style: solid; border-color: transparent; border-top-color: yellow; border-right-color: red; border-bottom-color: white; border-left-color: green; } HTML CSS OUTPUT

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Multiple gradients

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Complex graphics of a single DIV a.singlediv.com

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Animated graphics codepen.io/hakimel/pen/aIhkf

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Interactive UI

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On :target

.login { display: none; } .login:target { display: block; } HTML CSS OUTPUT

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Checkbox hack

.menu-view, .menu-state { display: none; } .menu-state:checked + .menu-view { display: block; } HTML CSS

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Checkbox hack • Custom Radio Buttons and Checkboxes • Tree menu • Tabbed areas • Dropdown menus • Push Toggles

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What you shall not do with CSS

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Avoid CSS inline styles

lorem ipsum

lorem ipsum HTML

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Do not use IDs for styling BAD

  #widget { border: 1px solid #357ebd; } GOOD

  .widget { border: 1px solid #357ebd; } CSS CSS

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Never use !important reactively BAD .toolbar .btn { border: none !important; } .btn { border: 1px solid #357ebd; width: 200px; }  CSS

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Do not override styles, but extend BAD .btn { border: 1px solid #357ebd; width: 200px; }   .toolbar .btn { border: none; } GOOD .btn { width: 200px; }   .btn-outlined { border: 1px solid #357ebd; } CSS CSS

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How you shall deal with CSS

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Be aware that browsers read selectors from right to left

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.feed nav ul li h2 CSS

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h2 h2 h2 h2 h2 h2 h2 h2 h2 li li li li li li li li li li ul ul ul u nav nav CSS

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h2 h2 h2 h2 h2 h2 h2 h2 h2 li li li li li li li li li li ul ul ul u nav nav .feed CSS

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h2 h2 h2 h2 h2 h2 h2 h2 h2 li li li li li li li li li li ul ul ul u nav nav .feed CSS

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.feed nav ul li h2 .feed-heading CSS

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Use relative typography

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/* Global scope */ html { font-size: 62.5%; /* 10px */ } /* Components */ .header { font-size: 1.6rem; } /* scale with components */ h1 { font-size: 2em; } Lorem ipsum Lorem ipsum 16px h1: 32px .header CSS OUTPUT

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/* Global scope */ @media (max-width: 960px) { html { font-size: 56.25%; /*9px*/ } } /* Components */ .header { font-size: 1.6rem; } /* scale with components */ h1 { font-size: 2em; } Lorem ipsum Lorem ipsum 14.4px h1: 28.8px .header CSS OUTPUT

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Split your CSS into modules

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@import "./main-menu.css"; @import "./panel.css"; MAIN.CSS PANEL.CSS /* Here go style for panel widget only */ .panel { } BUTTONS.CSS /* Here go styles for any buttons used in the project */ .btn { } @import "./buttons.css";