CSS

//HTML
<div class="container">
  <div class="star-widget">
    <input type="radio" name="rate" id="rate-5" />
    <label for="rate-5" class="fas fa-star"></label>
    <input type="radio" name="rate" id="rate-4" />
    <label for="rate-4" class="fas fa-star"></label>
    <input type="radio" name="rate" id="rate-3" />
    <label for="rate-3" class="fas fa-star"></label>
    <input type="radio" name="rate" id="rate-2" />
    <label for="rate-2" class="fas fa-star"></label>
    <input type="radio" name="rate" id="rate-1" />
    <label for="rate-1" class="fas fa-star"></label>
 </div>
</div>


//CSS
html,
body {
  display: grid;
  height: 100%;
  place-items: center;
  text-align: center;
  background-color: rgb(16, 16, 16);
}

.container {
  width: 400px;
  background-color: #111;
  padding: 20px 30px;
  border: 1px solid #444;
  border-radius: 5px;
  display: flex;
  align-items: center;
  justify-content: center;
}

/* STARS */
.star-widget input {
  display: none;
}

.star-widget label {
  font-size: 40px;
  color: #444;
  padding: 10px;
  float: right;
  cursor: pointer;
  transition: all 0.2s ease;
}

input:not(:checked) ~ label:hover,
input:not(:checked) ~ label:hover ~ label {
  color: #fd4;
}
input:checked ~ label {
  color: #fd4;
}

input#rate-5:checked ~ label {
  color: #fe7;
  text-shadow: 0 0 20px #952;
}

/* http://meyerweb.com/eric/tools/css/reset/
   v2.0-modified | 20110126
   License: none (public domain)
*/

html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed,
figure, figcaption, footer, header, hgroup,
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
  margin: 0;
	padding: 0;
	border: 0;
	font-size: 100%;
	font: inherit;
	vertical-align: baseline;
}

/* make sure to set some focus styles for accessibility */
:focus {
    outline: 0;
}

/* HTML5 display-role reset for older browsers */
article, aside, details, figcaption, figure,
footer, header, hgroup, menu, nav, section {
	display: block;
}

body {
	line-height: 1;
}

ol, ul {
	list-style: none;
}

blockquote, q {
	quotes: none;
}

blockquote:before, blockquote:after,
q:before, q:after {
	content: '';
	content: none;
}

table {
	border-collapse: collapse;
	border-spacing: 0;
}

input[type=search]::-webkit-search-cancel-button,
input[type=search]::-webkit-search-decoration,
input[type=search]::-webkit-search-results-button,
input[type=search]::-webkit-search-results-decoration {
    -webkit-appearance: none;
    -moz-appearance: none;
}

input[type=search] {
    -webkit-appearance: none;
    -moz-appearance: none;
    -webkit-box-sizing: content-box;
    -moz-box-sizing: content-box;
    box-sizing: content-box;
}

textarea {
    overflow: auto;
    vertical-align: top;
    resize: vertical;
}

/**
 * Correct `inline-block` display not defined in IE 6/7/8/9 and Firefox 3.
 */

audio,
canvas,
video {
    display: inline-block;
    *display: inline;
    *zoom: 1;
    max-width: 100%;
}

/**
 * Prevent modern browsers from displaying `audio` without controls.
 * Remove excess height in iOS 5 devices.
 */

audio:not([controls]) {
    display: none;
    height: 0;
}

/**
 * Address styling not present in IE 7/8/9, Firefox 3, and Safari 4.
 * Known issue: no IE 6 support.
 */

[hidden] {
    display: none;
}

/**
 * 1. Correct text resizing oddly in IE 6/7 when body `font-size` is set using
 *    `em` units.
 * 2. Prevent iOS text size adjust after orientation change, without disabling
 *    user zoom.
 */

html {
    font-size: 100%; /* 1 */
    -webkit-text-size-adjust: 100%; /* 2 */
    -ms-text-size-adjust: 100%; /* 2 */
}

/**
 * Address `outline` inconsistency between Chrome and other browsers.
 */

a:focus {
    outline: thin dotted;
}

/**
 * Improve readability when focused and also mouse hovered in all browsers.
 */

a:active,
a:hover {
    outline: 0;
}

/**
 * 1. Remove border when inside `a` element in IE 6/7/8/9 and Firefox 3.
 * 2. Improve image quality when scaled in IE 7.
 */

img {
    border: 0; /* 1 */
    -ms-interpolation-mode: bicubic; /* 2 */
}

/**
 * Address margin not present in IE 6/7/8/9, Safari 5, and Opera 11.
 */

figure {
    margin: 0;
}

/**
 * Correct margin displayed oddly in IE 6/7.
 */

form {
    margin: 0;
}

/**
 * Define consistent border, margin, and padding.
 */

fieldset {
    border: 1px solid #c0c0c0;
    margin: 0 2px;
    padding: 0.35em 0.625em 0.75em;
}

/**
 * 1. Correct color not being inherited in IE 6/7/8/9.
 * 2. Correct text not wrapping in Firefox 3.
 * 3. Correct alignment displayed oddly in IE 6/7.
 */

legend {
    border: 0; /* 1 */
    padding: 0;
    white-space: normal; /* 2 */
    *margin-left: -7px; /* 3 */
}

/**
 * 1. Correct font size not being inherited in all browsers.
 * 2. Address margins set differently in IE 6/7, Firefox 3+, Safari 5,
 *    and Chrome.
 * 3. Improve appearance and consistency in all browsers.
 */

button,
input,
select,
textarea {
    font-size: 100%; /* 1 */
    margin: 0; /* 2 */
    vertical-align: baseline; /* 3 */
    *vertical-align: middle; /* 3 */
}

/**
 * Address Firefox 3+ setting `line-height` on `input` using `!important` in
 * the UA stylesheet.
 */

button,
input {
    line-height: normal;
}

/**
 * Address inconsistent `text-transform` inheritance for `button` and `select`.
 * All other form control elements do not inherit `text-transform` values.
 * Correct `button` style inheritance in Chrome, Safari 5+, and IE 6+.
 * Correct `select` style inheritance in Firefox 4+ and Opera.
 */

button,
select {
    text-transform: none;
}

/**
 * 1. Avoid the WebKit bug in Android 4.0.* where (2) destroys native `audio`
 *    and `video` controls.
 * 2. Correct inability to style clickable `input` types in iOS.
 * 3. Improve usability and consistency of cursor style between image-type
 *    `input` and others.
 * 4. Remove inner spacing in IE 7 without affecting normal text inputs.
 *    Known issue: inner spacing remains in IE 6.
 */

button,
html input[type="button"], /* 1 */
input[type="reset"],
input[type="submit"] {
    -webkit-appearance: button; /* 2 */
    cursor: pointer; /* 3 */
    *overflow: visible;  /* 4 */
}

/**
 * Re-set default cursor for disabled elements.
 */

button[disabled],
html input[disabled] {
    cursor: default;
}

/**
 * 1. Address box sizing set to content-box in IE 8/9.
 * 2. Remove excess padding in IE 8/9.
 * 3. Remove excess padding in IE 7.
 *    Known issue: excess padding remains in IE 6.
 */

input[type="checkbox"],
input[type="radio"] {
    box-sizing: border-box; /* 1 */
    padding: 0; /* 2 */
    *height: 13px; /* 3 */
    *width: 13px; /* 3 */
}

/**
 * 1. Address `appearance` set to `searchfield` in Safari 5 and Chrome.
 * 2. Address `box-sizing` set to `border-box` in Safari 5 and Chrome
 *    (include `-moz` to future-proof).
 */

input[type="search"] {
    -webkit-appearance: textfield; /* 1 */
    -moz-box-sizing: content-box;
    -webkit-box-sizing: content-box; /* 2 */
    box-sizing: content-box;
}

/**
 * Remove inner padding and search cancel button in Safari 5 and Chrome
 * on OS X.
 */

input[type="search"]::-webkit-search-cancel-button,
input[type="search"]::-webkit-search-decoration {
    -webkit-appearance: none;
}

/**
 * Remove inner padding and border in Firefox 3+.
 */

button::-moz-focus-inner,
input::-moz-focus-inner {
    border: 0;
    padding: 0;
}

/**
 * 1. Remove default vertical scrollbar in IE 6/7/8/9.
 * 2. Improve readability and alignment in all browsers.
 */

textarea {
    overflow: auto; /* 1 */
    vertical-align: top; /* 2 */
}

/**
 * Remove most spacing between table cells.
 */

table {
    border-collapse: collapse;
    border-spacing: 0;
}

html,
button,
input,
select,
textarea {
    color: #222;
}


::-moz-selection {
    background: #b3d4fc;
    text-shadow: none;
}

::selection {
    background: #b3d4fc;
    text-shadow: none;
}

img {
    vertical-align: middle;
}

fieldset {
    border: 0;
    margin: 0;
    padding: 0;
}

textarea {
    resize: vertical;
}

.chromeframe {
    margin: 0.2em 0;
    background: #ccc;
    color: #000;
    padding: 0.2em 0;
}

//HTML
<div class="slider">
        <div class="slide"><img src="img/img-1.jpg" alt="Photo 1" /></div>
        <div class="slide"><img src="img/img-2.jpg" alt="Photo 2" /></div>
        <div class="slide"><img src="img/img-3.jpg" alt="Photo 3" /></div>
        <div class="slide"><img src="img/img-4.jpg" alt="Photo 4" /></div> 
</div>


//CSS
/* SLIDER */
.slider {
  max-width: 100rem;
  height: 50rem;
  margin: 0 auto;
  position: relative;

  /* To hide unwanted .slide */
  overflow: hidden;
}

.slide {
  position: absolute;
  top: 0;
  width: 100%;
  height: 50rem;

  display: flex;
  align-items: center;
  justify-content: center;

  /* THIS creates the animation! */
  transition: transform 1s;
}


//JS
//Slider
const slides = document.querySelectorAll('.slide');
const btnLeft = document.querySelector('.slider__btn--left');
const btnRight = document.querySelector('.slider__btn--right');

// Set a current slide to begin with
let currentSlide = 0;
//Set a maximum number of slides else number will be infite
const maxSlide = slides.length;

const goToSlide = slide => {
  //Change position for each slide
  slides.forEach((s, i) => {
    //e. currentSlide 1: 100 * (0 - 1) = -100% each item slides left
    s.style.transform = `translateX(${100 * (i - slide)}%)`;
  });
};

//Show slide on position 0
goToSlide(0);

//Next slide
const nextSlide = () => {
  //Reset the value once we reach max
  currentSlide === maxSlide - 1
    ? (currentSlide = 0)
    : //Increase by one everytime we click 'next'
      currentSlide++;

  goToSlide(currentSlide);
};

const prevSlide = () => {
  //If it is in position 0 then by pressing prev go to the last slide
  currentSlide === 0 ? (currentSlide = maxSlide - 1) : currentSlide--;
  goToSlide(currentSlide);
};

btnRight.addEventListener('click', nextSlide);
btnLeft.addEventListener('click', prevSlide);

//Handle keyboar event left-right
document.addEventListener('keydown', function (e) {
  if (e.key === 'ArrowRight') nextSlide();
  //Also with short-circuting
  e.key === 'ArrowLeft' && nextSlide();
});

h1 {
  font-size: 72px;
  background: -webkit-linear-gradient(#eee, #333);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

//HTML
<section>
  <div>
  	<p>
  		Some Text
    </p>
  </div>
</section>

<button id="toggle-button">Click Me</button>

//CSS
div {
    overflow:hidden;
    transition:height 0.3s ease-out;
    height:auto;
  }

//JS
function collapseSection(element) {
  // get the height of the element's inner content, regardless of its actual size
  var sectionHeight = element.scrollHeight;
  
  // temporarily disable all css transitions
  var elementTransition = element.style.transition;
  element.style.transition = '';
  
  // on the next frame (as soon as the previous style change has taken effect),
  // explicitly set the element's height to its current pixel height, so we 
  // aren't transitioning out of 'auto'
  requestAnimationFrame(function() {
    element.style.height = sectionHeight + 'px';
    element.style.transition = elementTransition;
    
    // on the next frame (as soon as the previous style change has taken effect),
    // have the element transition to height: 0
    requestAnimationFrame(function() {
      element.style.height = 0 + 'px';
    });
  });
  
  // mark the section as "currently collapsed"
  element.setAttribute('data-collapsed', 'true');
}

function expandSection(element) {
  // get the height of the element's inner content, regardless of its actual size
  var sectionHeight = element.scrollHeight;
  
  // have the element transition to the height of its inner content
  element.style.height = sectionHeight + 'px';

  // when the next css transition finishes (which should be the one we just triggered)
  element.addEventListener('transitionend', function(e) {
    // remove this event listener so it only gets triggered once
    element.removeEventListener('transitionend', arguments.callee);
    
    // remove "height" from the element's inline styles, so it can return to its initial value
    element.style.height = null;
  });
  
  // mark the section as "currently not collapsed"
  element.setAttribute('data-collapsed', 'false');
}


document.querySelector('#toggle-button').addEventListener('click', function(e) {
  var section = document.querySelector('div');
  var isCollapsed = section.getAttribute('data-collapsed') === 'true';
    
  if(isCollapsed) {
    expandSection(section)
    section.setAttribute('data-collapsed', 'false')
  } else {
    collapseSection(section)
  }
});

/**
 * Enable smooth scrolling on the whole document
 */
html {
	scroll-behavior: smooth;
}


/** Animations can cause issues for users who suffer from motion sickness and other conditions.
 * Disable smooth scrolling when users have prefers-reduced-motion enabled
 */
@media screen and (prefers-reduced-motion: reduce) {
	html {
		scroll-behavior: auto;
	}
}

//Pictures
 <picture>
       <source
    media="(max-width:599px) and (prefers-color-scheme: light)"
    srcset="images/bg-mobile-light.jpg"
    />
      <source
    media="(max-width:599px) and (prefers-color-scheme: dark)"
    srcset="images/bg-mobile-dark.jpg"
    />
      <source
    media="(min-width:600px) and (prefers-color-scheme: light)"
    srcset="images/bg-desktop-light.jpg"
    />
      <source
    media="(min-width:600px) and (prefers-color-scheme: dark)"
    srcset="images/bg-desktop-dark.jpg"
    />
      <img
    src="images/bg-mobile-light.jpg"
    aria-hidden="true"
    class="background-img"
    alt=""
    />
</picture>

//CSS
@media (prefers-color-scheme: dark) {
  :root {
    --color-primary: #25273c;
    --color-primary-text: #e4e5f1;
    --color-secondary-text: #cacde8;
    --color-deleted-text: #4d5067;
    --color-circle: #777a92;
    --color-background: #161722;
    --color-background-hover: #1c1e35;
  }
}

@media (prefers-color-scheme: light) {
  :root {
    --color-white: #ffffff;
    --color-primary: #ffffff;
    --color-primary-text: #494c6b;
    --color-secondary-text: #9394a5;
    --color-light-text: #d4d4d4;
    --color-active: #3a7cfd;
    --color-circle: #d6d6d6;
    --color-background: #fafafa;
    --color-background-hover: #ebebeb;
    --color-background-modal: rgba(73, 76, 107, 0.6);
    --color-error: #cd1237;
  }
}


//JS
let dark = window.matchMedia('(prefers-color-scheme: dark)').matches;
//Show which prefers-color-scheme user has before the page loads
window.matchMedia('(prefers-color-scheme: dark)');
if (dark) {
  //Do something
} else {
  //Do something
}

//if the primary input mechanism system of the device can hover over elements with ease, we use hover
@media (hover: hover) {
    /* ... */
}

//if the primary input mechanism system of the device cannot hover over elements with ease or they can but not easily (for example a long touch is performed to emulate the hover) or there is no primary input mechanism at all, we use none
@media (hover: none) {
    /* ... */
}

// By default, browsers will “skip” areas where the “ink” of a character crosses an underline. You can change this behavior to force the underline/overline to go through the character by setting text-decoration-skip-ink to none.

a:not([class]) {
	text-decoration-skip-ink: auto; // || none
}

.link {
  /* These are technically the same, but use both */
  overflow-wrap: break-word;
  word-wrap: break-word;

  word-break: break-word;

  /* Adds a hyphen where the word breaks, if supported (No Blink) */
  hyphens: auto;
}