:root {
  --ink: #1d2b36;
  --blue: #2a4f6f;
  --muted: #778899;
  --line: #b2bcc6;
  --paper: #ffffff;
  --wash: #f4f7f9;
  --success: #23643d;
  --success-bg: #e8f5eb;
  --error: #8a2530;
  --error-bg: #fbeaec;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--paper);
  color: var(--ink);
  border-top: 3px solid var(--blue);
  font-family: Arial, Helvetica, sans-serif;
  line-height: 1.6;
}

#header {
  min-height: 64px;
  padding: 14px 32px;
  border-bottom: 1px dotted var(--line);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.logo {
  color: var(--blue);
  font: bold 1.35rem Georgia, "Times New Roman", serif;
  text-decoration: none;
}

.slogan {
  color: var(--muted);
  font: 1.05rem Georgia, "Times New Roman", serif;
}

#content {
  margin: 32px 40px 48px 280px;
  max-width: 900px;
}

#nav {
  position: absolute;
  top: 96px;
  left: 28px;
  width: 220px;
}

#nav h2,
h1,
h2 {
  color: var(--blue);
  font-family: Georgia, "Times New Roman", serif;
}

h1 {
  margin-top: 0;
  font-size: 1.9rem;
}

h2 {
  margin-top: 1.5em;
  font-size: 1.2rem;
}

#nav h2 {
  margin: 0 0 8px;
  padding-bottom: 6px;
  border-bottom: 1px dotted var(--line);
  font-size: 1.05rem;
}

#nav ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

#nav li {
  border-bottom: 1px dotted var(--line);
}

#nav a {
  display: block;
  padding: 8px 6px;
  color: var(--blue);
  text-decoration: none;
}

#nav a:hover,
#nav a:focus-visible,
#nav a[aria-current="page"] {
  background: var(--wash);
  color: #102c44;
}

#nav a[aria-current="page"] {
  font-weight: bold;
}

.menu-horizontal {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.menu-horizontal a {
  display: block;
  padding: 6px 10px;
  border: 1px solid var(--line);
  color: var(--blue);
  text-decoration: none;
}

.menu-horizontal a[aria-current="page"] {
  background: var(--wash);
  font-weight: bold;
}

#footer {
  margin: 0 40px 0 280px;
  padding: 16px 0 24px;
  border-top: 1px dotted var(--line);
  color: var(--blue);
  text-align: center;
  font: 0.9rem Georgia, "Times New Roman", serif;
}

form {
  max-width: 620px;
  padding: 20px;
  border: 1px solid #d4dce3;
  background: var(--wash);
}

label {
  display: block;
  margin: 10px 0 4px;
  font-weight: bold;
}

input,
select,
textarea,
button {
  width: 100%;
  padding: 9px 10px;
  border: 1px solid #9cabb7;
  border-radius: 2px;
  color: var(--ink);
  font: inherit;
}

textarea {
  resize: vertical;
}

button {
  margin-top: 18px;
  border-color: var(--blue);
  background: var(--blue);
  color: white;
  cursor: pointer;
}

button:hover,
button:focus-visible {
  background: #1d3c56;
}

.message,
.note,
.date-card,
.task-card {
  margin: 16px 0;
  padding: 14px 18px;
  border-left: 4px solid var(--blue);
  background: var(--wash);
}

.message.success {
  border-color: var(--success);
  background: var(--success-bg);
  color: var(--success);
}

.message.error {
  border-color: var(--error);
  background: var(--error-bg);
  color: var(--error);
}

.message ul {
  margin-bottom: 0;
}

.date-card h2,
.task-card h2 {
  margin-top: 0;
}

.inline-form {
  display: grid;
  grid-template-columns: minmax(130px, 1fr) minmax(120px, 180px) 160px;
  align-items: end;
  gap: 10px;
  max-width: none;
}

.inline-form label,
.inline-form button {
  margin: 0;
}

.compact-form {
  display: grid;
  grid-template-columns: repeat(3, minmax(120px, 1fr));
  gap: 8px 16px;
}

.compact-form button {
  grid-column: 1 / -1;
}

.table-scroll {
  margin-top: 22px;
  overflow-x: auto;
}

.multiplication-table {
  border-collapse: collapse;
  min-width: 360px;
}

.multiplication-table th,
.multiplication-table td {
  min-width: 54px;
  padding: 10px;
  border: 1px solid #7b8c99;
  text-align: center;
}

code {
  padding: 0.1em 0.3em;
  background: var(--wash);
}

@media (max-width: 800px) {
  #header {
    padding-inline: 20px;
  }

  #nav {
    position: static;
    width: auto;
    margin: 20px;
  }

  #nav ul {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 4px 12px;
  }

  #content,
  #footer {
    margin-inline: 20px;
  }

  .inline-form,
  .compact-form {
    display: block;
  }
}

@media (max-width: 480px) {
  #header {
    align-items: flex-start;
    flex-direction: column;
    gap: 2px;
  }

  #nav ul {
    grid-template-columns: 1fr;
  }
}