My basic css style

base.css

/* -------------------------------------------------------------------------------------- */
/* BASIC SETUP */
/* -------------------------------------------------------------------------------------- */
* {
  /* default css reset */
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

*:focus {
  outline: none;
}
/* removes browser focus effect on inputs etc   */
body,
html {
  /* default html rules */
  background-color: #F4F4F4;
  color: #555;
  font-family: -apple-system, BlinkMacSystemFont, Roboto, 'Helvetica Neue', Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI', 'Segoe UI Emoji', 'Segoe UI Symbol', 'Meiryo UI';
  /* main google font plus alternatives */
  font-size: 13px;
  font-weight: 300;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

.clearfix {
  zoom: 1;
}

.clearfix:after {
  content: '.';
  clear: both;
  display: block;
  height: 0;
  visibility: hidden;
}

.left {
  float: left;
}

.right {
  float: right;
}
/* -------------------------------------------------------------------------------------- */
/* REUSABLE COMPONENTS */
/* -------------------------------------------------------------------------------------- */
.row {
  /* fluid row rules */
  max-width: 1140px;
  margin: 0 auto;
}

section {
  padding-top: 2%;
  height: 100vh;
}


.full_height {
  height: 80vh;
}

.rounded-image {

}

.formatted-text {
  p + p {
    margin-top: 1em;
  }
}

/* ----------- BOXES ----------- */
.box {
  background-color: #fff;
  border-radius: 5px;
  box-shadow: 0 2px 2px #efefef;
  margin-bottom: 15px;
  padding: 3% 3%;
}

.bottom-action-bar {
  width: 100%;
}

.bottom-action-bar:before {
  display: block;
  height: 1px;
  background-color: lightgray;
  content: "";
  margin: 30px auto;
}

.bottom-action-bar .left {
  float: left;
}

.bottom-action-bar .right {
  float: right;
}

.right {
  float: right;
}

/* ----------- HEADINGS ----------- */
h1,
h2,
h3 {
  font-weight: bold;
  /* reduce font weigth for bigger font sizes */
  // text-transform: uppercase;
}

h1 {
  margin: 0;
  /* reset normalize rule */
  margin-bottom: 20px;
  color: #fff;
  font-size: 240%;
  /* relative to 20px in HTML rule */
  word-spacing: 4px;
  letter-spacing: 1px;
}

h2 {
  font-size: 160%;
  word-spacing: 2px;
  margin-bottom: 30px;
  letter-spacing: 1px;
  text-transform: uppercase;
}

h2:after {
  display: block;
  height: 2px;
  background-color: #e7eaec;
  content: "";
  width: 100%;
  margin: 20px auto 0;
}

h3 {
  font-size: 110%;
  margin-bottom: 15px;
}

.centered {
  width: 90%;
  margin: 0 auto;
}

/* ----------- ICONS ----------- */
.icon-small {
  width: 17px;
  margin-right: 5px;
}

.icon-big {
  font-size: 350%;
  display: block;
  color: #e67e22;
  margin-bottom: 10px;
}
/* ----------- LINKS ----------- */
a:link,
a:visited {
  color: #BB362F;
  text-decoration: none;
  padding-bottom: 1px;
  border-bottom: 1px solid #BB362F;
  -webkit-transition: border-bottom 0.2s, color 0.2s;
  transition: border-bottom 0.2s, color 0.2s;
}

a:active,
a:hover {
  color: #555;
  border-bottom: 1px solid transparent;
}
/* ----------- BUTTONS ----------- */
.btn:link,
.btn:visited,
input[type=submit],
button[type=submit] {
  display: inline-block;
  /* dont force linebreak like block elements, but can have margin and padding */
  padding: 10px 30px;
  font-weight: 300;
  text-decoration: none;
  border-radius: 3px;
  color: #BB362F;
  -webkit-transition: background-color 0.2s, border 0.2s, color 0.2s;
  transition: background-color 0.2s, border 0.2s, color 0.2s;
  /*  */
}

.btn-full:link,
.btn-full:visited,
input[type=submit],
button[type=submit] {
  background-color: #BB362F;
  border: 1px solid #BB362F;
  color: #fff;
  margin-right: 15px;
}

.btn-ghost:link,
.btn-ghost:visited {
  border: 1px solid #BB362F;
}

.btn:active,
.btn:hover,
input[type=submit]:active,
input[type=submit]:hover,
button[type=submit]:active,
button[type=submit]:hover {
  background-color: #992924;
}

.btn-full:active,
.btn-full:hover,
input[type=submit]:active,
input[type=submit]:hover,
button[type=submit]:active,
button[type=submit]:hover {
  border: 1px solid #992924;
}

.btn-ghost:active,
.btn-ghost:hover {
  border: 1px solid #992924;
  color: #fff;
}

.btn.disabled,
input[type=submit].disabled,
button[type=submit].disabled {
  border-color: #BBBBBB;
  background-color: #BBBBBB;
  cursor: default;
}

input[type=submit],
button[type=submit] {
  font-weight: normal;
}

input[type=submit]:hover,
button[type=submit]:hover {
  cursor: pointer;
}
/* ----------- PARAGRAPHS ----------- */
.long-copy {
  line-height: 145%;
  width: 70%;
  margin-left: 15%;
  /* to center. 100 % - 70% of width = 30% /2 = 15% */
}
/* -------------------------------------------------------------------------------------- */
/* FORM */
/* -------------------------------------------------------------------------------------- */
.default-form {
  width: 100%;
  margin: 0 auto;
}

input[type=email],
input[type=text],
select,
textarea {
  width: 100%;
  padding: 7px;
  border-radius: 3px;
  border: 1px solid #ccc;
}

textarea {
  height: 100px;
}

input[type=checkbox] {
  margin: 10px 5px 1px 0;
}