* {
  box-sizing: border-box;
}

:root {
  --bg-color: #f5f5f5;
  --text-color: #000000;
  --card-bg: #ffffff;
  --sidebar-bg: #000000;
  --sidebar-text: #ffffff;
  --shadow-color: lightgray;
  --border-color: #ccc;
  --accent-color: #000000;
  --accent-text: #ffffff;
}

body.dark-theme {
  --bg-color: #121212;
  --text-color: #e0e0e0;
  --card-bg: #1e1e1e;
  --sidebar-bg: #1a1a1a;
  --sidebar-text: #e0e0e0;
  --shadow-color: #000000;
  --border-color: #333;
  --accent-color: #ffffff;
  --accent-text: #000000;
}

body {
  margin: 0;
  font-family: Arial, sans-serif;
  background: var(--bg-color);
  color: var(--text-color);
}

.app {
  display: grid;
  grid-template-columns: 220px 1fr;
}

/* SIDEBAR */
.sidebar {
  background: var(--sidebar-bg);
  color: var(--sidebar-text);
  padding: 20px;
  height: 100vh;
}

.logo {
  font-size: 20px;
  margin-bottom: 30px;
}

.nav-item {
  display: flex;
  gap: 10px;
  padding: 10px;
  color: var(--sidebar-text);
  text-decoration: none;
}

.nav-item img {
  width: 18px;
  filter: invert(1);
}

.nav-item:hover {
  background: #333;
}

/* MAIN */
.main {
  padding: 20px;
}

.topbar {
  display: flex;
  justify-content: space-between;
}

/* BUTTON */
.add-btn {
  background: var(--accent-color);
  color: var(--accent-text);
  padding: 10px 16px;
  border-radius: 6px;
  text-decoration: none;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  font-size: 14px;
}

.add-btn img {
  width: 16px;
  filter: invert(var(--img-invert, 1));
}

body.dark-theme .add-btn img {
  filter: invert(0);
}

/* CARDS */
.content {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  margin-top: 20px;
}

.card {
  background: var(--card-bg);
  padding: 20px;
  border-radius: 10px;
  box-shadow: 0 4px 10px var(--shadow-color);
}

/* HABIT CARD */
.habit-card {
  background: var(--card-bg);
  padding: 15px;
  border-radius: 10px;
  box-shadow: 0 2px 5px var(--shadow-color);
}

/* CALENDAR */
.calendar {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 10px;
}

.day {
  background: var(--card-bg);
  padding: 10px;
  text-align: center;
  border: 1px solid var(--border-color);
}

/* AUTH PAGES */

.auth-container {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background: var(--bg-color);
}

.auth-card {
  background: var(--card-bg);
  padding: 30px;
  border-radius: 10px;
  width: 300px;
  box-shadow: 0 4px 10px var(--shadow-color);
}

.auth-card h2 {
  margin-bottom: 20px;
}

.auth-card input,
.auth-card select {
  width: 100%;
  padding: 10px;
  margin-bottom: 12px;
}

.auth-btn {
  width: 100%;
  padding: 10px;
  background: var(--accent-color);
  color: var(--accent-text);
  border: none;
  border-radius: 6px;
  cursor: pointer;
}

/* RESPONSIVE DESIGN */
@media (max-width: 768px) {
  .app {
    grid-template-columns: 1fr;
  }
  
  .sidebar {
    height: auto;
    padding: 15px;
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-between;
  }
  
  .logo {
    margin-bottom: 0px;
  }
  
  .nav {
    display: flex;
    overflow-x: auto;
    width: 100%;
    gap: 15px;
    margin-top: 15px;
    padding-bottom: 5px;
    scrollbar-width: none; /* Firefox */
  }
  
  .nav::-webkit-scrollbar {
    display: none; /* Chrome, Safari, Edge */
  }
  
  .nav-item {
    font-size: 14px;
    white-space: nowrap;
  }
  
  .content {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 480px) {
  .content {
    grid-template-columns: 1fr;
  }
  
  .topbar {
    flex-direction: column;
    gap: 15px;
    align-items: stretch;
  }
  
  .add-btn {
    text-align: center;
  }
  
  .calendar {
    grid-template-columns: repeat(4, 1fr);
  }
}