/* ===============================
   Base & Typography
================================= */

:root {
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --success: #16a34a;
  --danger: #dc2626;
  --warning: #d97706;
  --info: #0284c7;

  --bg: #f8fafc;
  --card-bg: #ffffff;
  --border: #e2e8f0;
  --text: #1e293b;
  --text-muted: #64748b;

  --radius: 10px;
  --shadow: 0 4px 12px rgba(0,0,0,0.05);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  font-size: 14px;
  line-height: 1.6;
}

a {
  color: var(--primary);
  text-decoration: none;
}

a:hover {
  color: var(--primary-hover);
  text-decoration: underline;
}

/* ===============================
   Layout
================================= */

#main {
  max-width: 1100px;
  margin: 40px auto;
  padding: 0 20px;
}

#main h1 {
  font-size: 24px;
  font-weight: 600;
  margin-bottom: 10px;
}

#main h2.sub-title {
  font-size: 14px;
  color: var(--text-muted);
  margin-bottom: 25px;
}

#content {
  display: flex;
  gap: 30px;
  background: var(--card-bg);
  border-radius: var(--radius);
  padding: 25px;
  box-shadow: var(--shadow);
}

.left-part {
  width: 220px;
}

.central-part {
  flex: 1;
}

/* Responsive */
@media (max-width: 900px) {
  #content {
    flex-direction: column;
  }

  .left-part {
    width: 100%;
  }
}

/* ===============================
   Sidebar Menu
================================= */

.left-menu {
  list-style: none;
  padding: 0;
  margin: 0;
}

.left-menu li {
  margin-bottom: 8px;
  padding: 8px 12px;
  border-radius: 6px;
  cursor: pointer;
  transition: 0.2s ease;
}

.left-menu li:hover {
  background: #f1f5f9;
}

.left-menu li.current {
  background: var(--primary);
  color: white;
  font-weight: 500;
}

.left-menu li.passed {
  color: var(--success);
  font-weight: 500;
}

/* ===============================
   Forms
================================= */

.form_text,
.form_select {
  width: 100%;
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 14px;
  transition: 0.2s;
}

.form_text:focus,
.form_select:focus {
  border-color: var(--primary);
  outline: none;
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form_button {
  display: inline-block;
  padding: 8px 16px;
  border-radius: 8px;
  border: none;
  background: var(--primary);
  color: white;
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: 0.2s ease;
}

.form_button:hover {
  background: var(--primary-hover);
}

.form_button:active {
  transform: translateY(1px);
}

/* ===============================
   Alerts
================================= */

.alert {
  padding: 14px 16px;
  border-radius: var(--radius);
  margin-bottom: 16px;
  font-size: 14px;
}

.alert-success {
  background: #ecfdf5;
  border: 1px solid #bbf7d0;
  color: var(--success);
}

.alert-error {
  background: #fef2f2;
  border: 1px solid #fecaca;
  color: var(--danger);
}

.alert-warning {
  background: #fffbeb;
  border: 1px solid #fde68a;
  color: var(--warning);
}

.alert-info {
  background: #eff6ff;
  border: 1px solid #bfdbfe;
  color: var(--info);
}

/* ===============================
   Notes / Help Boxes
================================= */

.notes_container {
  display: none;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 15px;
  margin-top: 10px;
  box-shadow: var(--shadow);
}

.notes_container h4 {
  margin-top: 0;
  font-size: 14px;
  color: var(--primary);
}

.notes_container p {
  margin: 10px 0;
  color: var(--text-muted);
}

/* ===============================
   Content Text
================================= */

.text h1,
.text h2,
.text h3,
.text h4 {
  margin-bottom: 10px;
  font-weight: 600;
}

.text span.date {
  font-size: 12px;
  color: var(--text-muted);
}

.text span.sub,
.text a.sublink {
  font-size: 12px;
  color: var(--text-muted);
}

/* ===============================
   Footer
================================= */

#footer {
  margin-top: 40px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 13px;
}