/* =========================================================
   Lab 3 CSS - FINAL VERSION (VALIDATOR SAFE)
   ========================================================= */

/* CSS variables */
:root {
  --main-color: #2c3e50;
  --card-bg: #ffffff;
  --soft-border: #cccccc;
  --accent-color: #4a6fa5;
}

/* universal selector */
* {
  box-sizing: border-box;
}

/* element selector */
body {
  font-family: 'Roboto', sans-serif;
  background-color: #f5f5f5;
  color: rgb(40, 40, 40);
  margin: 0;
  padding: 0;
  line-height: 1.5;
  font-size: 16px;
}

/* selector list */
h1,
h2 {
  font-weight: bold;
}

/* id selector */
#main-title {
  color: var(--main-color, blue);
  text-decoration: underline;
  font-size: 2rem;
  margin-bottom: 0.5em;
}

/* class selector */
.highlight {
  color: orange;
}

/* paragraph */
p {
  color: rgba(20, 20, 20, 0.9);
}

/* hsl + hsla */
h1 {
  color: hsl(210, 60%, 35%);
}

h2 {
  color: hsla(260, 60%, 40%, 0.95);
}

/* color example */
.color-test {
  color: purple;
  background-color: #e6f2ff;
  padding: 0.5rem;
  border-radius: 8px;
}

/* header */
.page-header {
  background-color: #ffffff;
  position: sticky;
  top: 0;
  z-index: 10;
}

/* section box model */
section {
  margin-top: 10px;
  margin-right: 20px;
  margin-bottom: 10px;
  margin-left: 20px;

  padding-top: 12px;
  padding-right: 18px;
  padding-bottom: 12px;
  padding-left: 18px;

  border-style: solid;
  border-color: var(--soft-border, gray);
  border-width: 2px;
  border-radius: 12px;
}

/* main layout */
main {
  margin: 20px auto;
  padding: 20px;
  width: 80%;
  max-width: 1000px;
  min-width: 300px;
}

/* card */
.card {
  border: 2px solid #d8d8d8;
  background-color: var(--card-bg, #fff);
}

/* footer */
.page-footer {
  margin: 10pt 0 0 0;
  padding: 0.8rem;
  display: block;
}

/* image */
.media-image {
  width: 300px;
  height: auto;
  max-width: 100%;
  min-width: 12cm;
  border-radius: 10px;
}

/* display examples */
nav a {
  display: inline-block;
  padding: 5px;
  text-decoration: none;
}

.inline-chip {
  display: inline;
  background-color: #dceeff;
  border: 1px solid #7da6d8;
  padding: 0.2em 0.5em;
}

.hidden-note {
  display: none;
}

/* pseudo classes */
nav a:hover {
  color: red;
}

nav a:active {
  color: green;
}

button:hover {
  background-color: #ddd;
}

button:active {
  transform: scale(0.98);
}

/* attribute selector */
input[type="text"] {
  border: 2px solid blue;
}

/* combinators */
section p {
  line-height: 1.5;
}

ul > li {
  margin-bottom: 0.5rem;
}

h2 + p {
  font-style: italic;
}

h2 ~ ul {
  color: #333;
}

/* combined selector */
section.card {
  border-width: 3px;
}

/* ===== "Nested selector" requirement (VALID VERSION) ===== */
/* (using descendant selector instead of unsupported nesting) */
.media-panel h3 {
  color: #2d4f73;
  margin-left: 0.2em;
}

.media-panel p {
  font-size: 1.05em;
}

/* flexbox */
.nav-list {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  list-style: none;
  padding-left: 0;
  flex-wrap: wrap;
}

.task-flex {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  padding-left: 1rem;
}

.task-card {
  background-color: #f2f7ff;
  padding: 1rem;
  border: 1px solid #bfd1eb;
  border-radius: 10px;
  flex: 1 1 180px;
}

.attendance-container {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

/* grid */
.agenda-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  padding-left: 1.2rem;
}

.grid-item {
  background-color: #f9fbff;
  padding: 0.8rem;
  border: 1px solid #d6e2f0;
  border-radius: 10px;
}

/* nested-like example */
section.card p {
  color: #333;
}

/* form */
fieldset {
  padding: 1rem;
}

textarea {
  width: 85%;
  min-width: 240px;
}

/* responsive */
@media (max-width: 768px) {
  main {
    width: 95%;
  }

  .nav-list {
    flex-direction: column;
    align-items: flex-start;
  }

  .agenda-grid {
    grid-template-columns: 1fr;
  }

  .task-flex {
    flex-direction: column;
  }

  h1 {
    font-size: 1.8rem;
  }
}