index.css

/* http://meyerweb.com/eric/tools/css/reset/ 
   v2.0 | 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;
}
/* 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;
}


/* Main */

:root {
  --white: #fff;
  --calendar-background-color: #ffffff;
  --calendar-border-color: #e5e5e5;
  --calendar-weekend-color: #e5e5e580;
  --text-color: #333333;
  --today-color: #ff0000;
  --today-text-color: #ffffff;
  --calendar-max-width: 800px;
  --font-size: 14px;
  --font-family: 'Open Sans', sans-serif;
  --timeline-width: 60px;
  --calendar-cell-height: 40px;
  --calendar-cell-width: 106px;
  --calendar-body-height: 600px;
}

html {
  font-size: var(--font-size);
  font-family: var(--font-family);
  box-sizing: border-box;
}

button {
  cursor: pointer;
  background-color: var(--white);
  border: none;
  padding: .4rem;
  border-radius: .2rem;
  box-shadow: 0px 0px 0px 1px var(--calendar-border-color);
}

button:hover {
  box-shadow: 0px 0px 0px 2px var(--calendar-border-color);
}


.calendar-container {
  width: 100%;
  max-width: var(--calendar-max-width);
  margin: 1rem;
  height: 100%;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

.calendar-header {
  width: 100%;
  height: 50px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  background-color: var(--calendar-background-color);
}

.calendar-title-month {
  font-size: 1.5rem;
  font-weight: bold;
  color: var(--text-color);
}

.calendar-title-year {
  font-size: 1.5rem;
  font-weight: 200;
  margin-left: .4rem;
  color: var(--text-color);
}

.calendar {
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  background-color: var(--calendar-background-color);
}

.calendar-days {
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: row;
  align-items: center;
  background-color: var(--calendar-background-color);
  height: 3rem;
  border-bottom: 1px solid var(--calendar-border-color);
}

.calendar-days > .calendar-day {
  flex: 1;
  display: flex;
  align-content: center;
  justify-content: center;
  align-items: center;
  width: 10vw;
}

.calendar-day-number {
  width: 1.2rem;
  height: 1.2rem;
  line-height: 1.2rem;
  text-align: center;
}

.calendar-days > .calendar-timeline-column {
  flex: 1;
  max-width: var(--timeline-width);
}

.calendar-day > .calendar-day-number {
  margin-left: .4rem;
  padding: .4rem;
}

.calendar-day-number.calendar-day-number-today {
  background-color: var(--today-color);
  border-radius: 50%;
  color: var(--today-text-color);
}

.calendar-body{
  width: 100%;
  height: 100%;
  max-height: var(--calendar-body-height);
  overflow-y: auto;
  position: relative;
  background-color: var(--calendar-background-color);
}

.calendar-body-rows {
  width: 100%;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  position: relative;
}

.calendar-body-row {
  width: 100%;
  height: var(--calendar-cell-height);
  display: flex;
  flex-direction: row;
  align-items: center;
}


.calendar-body-column {
  flex: 1;
  height: 100%;
  display: flex;
  align-content: center;
  justify-content: center;
  align-items: center;
  border: 1px solid var(--calendar-border-color);
  position: relative;
  box-sizing: border-box;
  max-width: var(--calendar-cell-width);
  width: 10vw;
}


.calendar-body-column:nth-child(2) {
  border-left: none;
}

.calendar-body-column:last-child {
  border-right: none;
  background-color: var(--calendar-weekend-color);
}

.calendar-body-column:nth-last-child(2) {
  background-color: var(--calendar-weekend-color);
}

.calendar-timeline-column{
  color: var(--text-color);
  opacity: 0.5;
  margin-bottom: var(--calendar-cell-height);
}

.calendar-timeline-last-hour {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: space-between;
  height: calc(var(--calendar-cell-height) * 1.3);
  margin-bottom: calc(var(--calendar-cell-height) * -1);
}

.calendar-all-day-row {
  position: sticky;
  top: 0;
  width: 100%;
  border-bottom: 4px solid var(--calendar-border-color);
  height: calc(var(--calendar-cell-height) / 2);
  margin-bottom: 1rem;
  color: var(--text-color);
  background-color: var(--calendar-background-color);
  z-index: 1;
  display: flex;
}

.calendar-all-day-row > * {
  border-top: none;
  border-bottom: none;
}

.calendar-all-day-row > .calendar-body-column:nth-last-child(1), 
.calendar-all-day-row > .calendar-body-column:nth-last-child(2) {
  padding-top: var(--calendar-cell-height);
}

.calendar-all-day-row > .calendar-body-column::after {
  content: "";
  position: absolute;
  top: 0;
  right: -2px;
  width: 2px;
  height: var(--calendar-cell-height);
  background-color: var(--calendar-border-color);
}

.calendar-all-day-row > .calendar-timeline-column::after {
  display: none;
}

.calendar-body-column.calendar-timeline-column {
  max-width: var(--timeline-width);
  border: none;
}

.calendar-event {
  flex: 1;
  font-size: 0.6rem;
  font-weight: bold;
  text-overflow: ellipsis;
  white-space: nowrap;
  overflow: hidden;
  align-self: flex-start;
  border-radius: 2px;
  height: 100%;
  opacity: 0.8;
  position: relative;
}

.calendar-event:hover{
  cursor: pointer;
  opacity: 1;
  transform: scale(1.1);
  z-index: 2;
  transition: all 0.2s ease-in-out;
}


.calendar-body-column > .calendar-event:not(:last-child) {
  margin-right: 2px;
}

.calendar-event-tooltip {
  position: absolute;
  top: 0;
  left: 0;
  width: 300px;
  height: 150px;
  background-color: var(--calendar-background-color);
  border-radius: 4px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  z-index: 99;
  box-shadow:  0px 24px 38px 3px rgb(0 0 0 / 14%), 0px 9px 46px 8px rgb(0 0 0 / 12%), 0px 11px 15px -7px rgb(0 0 0 / 20%);
}

.calendar-event-tooltip-body {
  width: 100%;
  height: 100%;
  padding: 15px;
  padding-left: 45px;
  display: flex;
  flex-direction: column;
  justify-content: flex-start;
}

.calendar-event-tooltip-header{
  font-size: 1.2rem;
  font-weight: bold;
  margin-bottom: 1rem;
}

.calendar-event-tooltip-close {
  position: absolute;
  right: 15px;
}

.calendar-event-tooltip-close:hover {
  transform: scale(1.1);
  transition: all 0.2s ease-in-out;
  cursor: pointer;
}


@media (max-width: 768px) {
  .calendar-day-number{
    display: none;
  }
  .calendar-header {
    height: 40px;
  }
  .calendar-title-month {
    font-size: 1.2rem;
  }
  .calendar-title-year {
    font-size: 1.2rem;
  }
  .calendar-days {
    height: 2rem;
  }
  .calendar-day {
    width: 10vw;
  }
  .calendar-day-number {
    font-size: 1.2rem;
  }
  .calendar-body-column {
    max-width: var(--calendar-cell-width);
    width: 10vw;
  }
  .calendar-timeline-column {
    max-width: var(--timeline-width);
  }
  .calendar-timeline-last-hour {
    height: calc(var(--calendar-cell-height) * 1.3);
    margin-bottom: calc(var(--calendar-cell-height) * -1);
  }
  .calendar-all-day-row {
    height: calc(var(--calendar-cell-height) / 2);
  }
}