* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: "Segoe UI", sans-serif;
}

body {
  background: #f5f5f5;
}

/* APP LAYOUT */
.app {
  display: flex;
  height: 100vh;
}

/* SIDEBAR */
.sidebar {
  width: 220px;
  background: #ffffff;
  border-right: 2px solid #e5e5e5;
  padding: 20px;
}

.logo {
  font-size: 32px;
  font-weight: 900;
  color: #58cc02;
  margin-bottom: 30px;
}

.nav button {
  display: block;
  width: 100%;
  padding: 12px;
  margin-bottom: 10px;
  border-radius: 12px;
  border: none;
  background: none;
  text-align: left;
  font-weight: 700;
  cursor: pointer;
}

.nav button.active {
  background: #ddf4ff;
  color: #1cb0f6;
}

/* MAIN */
.main {
  flex: 1;
  padding: 30px;
}

/* CONTENT GRID */
.content {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: 30px;
}

/* UNIT COLUMN */
.unit-column {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

/* UNIT HEADER — WIDEST ELEMENT */
.unit-header {
  background: #58cc02;
  color: white;
  padding: 25px;
  border-radius: 18px;
  box-shadow: 0 6px 0 #46a302;
}

.unit-header h1 {
  font-size: 32px;
}

.unit-header p {
  opacity: 0.9;
}

/* LESSON TILE */
.lesson-tile {
  background: white;
  border-radius: 14px;
  padding: 16px 20px;
  display: flex;
  align-items: center;
  gap: 20px;
  cursor: pointer;
  border: 2px solid #e5e5e5;
}

.lesson-tile:hover {
  background: #f9f9f9;
}

.lesson-num {
  font-weight: 900;
}

.lesson-title {
  color: #666;
  font-size: 14px;
}

/* RIGHT COLUMN */
.right-column {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

/* STATS */
.stats-card {
  background: white;
  border-radius: 16px;
  padding: 16px;
  border: 2px solid #e5e5e5;
  display: flex;
  justify-content: space-between;
  font-weight: 700;
}

/* GENERIC CARD */
.card {
  background: white;
  border-radius: 16px;
  padding: 16px;
  border: 2px solid #e5e5e5;
}
/* LESSON OVERLAY */
.lesson-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 999;
}

.lesson-card {
  background: white;
  border-radius: 18px;
  padding: 24px;
  width: 600px;
  max-width: 90%;
}

.lesson-card pre {
  background: #1e1e1e;
  color: #a6e22e;
  padding: 16px;
  border-radius: 10px;
  margin: 16px 0;
  font-family: Consolas, monospace;
  white-space: pre-wrap;
}

.lesson-card button {
  background: #58cc02;
  color: white;
  border: none;
  padding: 12px 20px;
  border-radius: 12px;
  font-weight: 700;
  cursor: pointer;
}