styles.css

:root {
  --sidebar-width: 350px;
  --properties-height: 300px;
  --general-margin: 5px;

  --gray: #f0f0f0;
  --dark-gray: #333;
  --white: #fff;
  --primary-color: #0eac53;
}

body {
  margin: 0;

  background-color: var(--gray);
  font-family: 'Lato', sans-serif;
}

/* Utitlity classes */
.u-hidden {
  display: none;
}

/* Main layout */
.builder {
  align-items: Stretch;
  display: flex;
  min-height: 100vh;
  min-width: 100%;
  max-width: 100%;
}

.builder__main-area {
  display: flex;
  flex-direction: column;
  width: calc(100% - var(--sidebar-width));
  margin: var(--general-margin);
  margin-left: 0;
}

.builder__main-area__map {
  flex-grow: 1;
  flex-shrink: 0;
  height: calc(100% - var(--properties-height) - var(--general-margin) * 2);
  width: 100%;

  box-shadow: 0px 0px 2px 1px var(--gray);
}

.builder__main-area__properties {
  height: calc( var(--properties-height) - var(--general-margin) * 2);
  margin-top: var(--general-margin);
  width: 100%;

  background-color: var(--white);
  box-shadow: 0px 0px 25px 2px var(--gray);
}

.builder__main-area__properties:empty {
  content: 'Select a layer to edit its properties';
}

.builder__sidebar {
  flex-grow: 0;
  flex-shrink: 0;
  width: var(--sidebar-width);
  margin: var(--general-margin);
  max-height: calc(100vh - var(--general-margin) * 2);

  background-color: var(--white);
  box-shadow: 0px 0px 25px 2px var(--gray);
}

/* Color picker */
.color-picker {
  display: flex;
  justify-content: space-around;
}

.color-picker__option:not(:last-child) {
  padding-right: 2px;
}

.color-picker__option__color {
  border: 2px solid transparent;
  border-radius: 25px;
  height: 25px;
  width: 25px;

  cursor: pointer;
}

.color-picker__option__color.--is-selected {
  border-color: var(--dark-gray);
}

/* List of items */
.item-list {
  margin: 0;
  padding: 5px;

  list-style-type: none;
}

.item-list__item {
  border: 1px solid var(--gray);
  font-size: 14px;
  margin: 3px 0;
  padding: 5px;

  border-radius: 4px;
  color: var(--dark-gray);
  cursor: pointer;
}

.item-list__item:before {
  display: inline-block;
  width: 15px;

  content: '✔';
  visibility: hidden;
}

.item-list__item--is-selected {
  font-weight: bold;
}

.item-list__item:hover {
  background-color: #f5f5f5;
}

.item-list__item--is-selected:before {
  visibility: visible;
}

/* Layout for a sidebar */
.sidebar {
  display: flex;
  flex-direction: column;

  max-height: calc( 100vh - var(--general-margin) * 2);
}

.sidebar__element--has-list {
  flex-grow: 1;
  flex-shrink: 1;
  overflow: auto;
}

.sidebar__element--is-small {
  flex-shrink: 0;
  min-height: 117px;
  max-height: 300px;
}

.sidebar__element--is-fixed {
  flex-grow: 0;
  flex-shrink: 0;
}

/* Title */
.title {
  font-size: 18px;
  margin: 10px 0;

  text-align: center;
  font-weight: bold;
}

/* Group of buttons */
.button-list {
  display: flex;
  align-items: space-around;
}

.button-list__button {
  flex-grow: 1;
}

.button-list__button + .button-list__button {
  margin-right: 3px;
}

/* Single button */
.button {
  border: 1px solid var(--gray);
  margin: 5px;
  padding: 10px 0;

  background-color: var(--primary-color);
  border-radius: 4px;
  color: var(--white);
  cursor: pointer;
}

.button:hover {
  opacity: 0.9;
}

.button--is-secondary {
  border: 0 none;
  color: var(--dark-gray);

  background-color: white;
}

.button--is-disabled {
  pointer-events: none;
}

/* Properties layout */
.properties {
  border-collapse: collapse;
  display: table;
  table-layout: fixed;
  width: 100%;
}

.properties__pair {
  display: table-row;
  border-top: 1px solid var(--gray);
  border-bottom: 1px solid var(--gray);
}

.properties__key {
  display: table-cell;
  font-size: 14px;
  padding: 10px;
  width: 45px;
  vertical-align: middle;
}

.properties__value {
  border-left: 1px solid var(--gray);
  display: table-cell;
  text-align: right;
  padding: 10px;
  vertical-align: middle;
}

.properties__value--is-separator {
  letter-spacing: 0.6px;
  font-size: 13px;

  font-weight: bold;
  text-align: left;
  text-transform: uppercase;
}

.properties__group {
  display: table-row-group;
}

/* Input */
.input {
  box-sizing: border-box;
  width: 100%;
}

/* Image picker */
.image-picker__option {
  border:1px solid transparent;
  border-radius: 5px;
  cursor: pointer;
  padding: 5px;
}

.image-picker__option.--is-selected {
  border-color: var(--dark-gray);
}

/* Searchbox */
.searchbox {
  margin: 5px;
}

.searchbox__input {
  box-sizing: border-box;
  padding: 5px;
  width: 100%;
}

/* Placeholder that shows a single sentence */
.box-placeholder {
  margin: 50px 0;

  color: var(--dark-gray);
  font-size: 14px;
  font-style: italic;
  text-align: center;
}