:root {
    --bg-color: #1e2125;
    --card-color: #282c31;
    --accent-color: #6bf3d7;
    --text-color: #f0f0f0;
    --subtle-text-color: #a0a0a0;
    --shadow-color: rgba(0, 0, 0, 0.2);
    --sidebar-width: 80px;
    --border-radius: 16px; 
  }
  
  * {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
  }
  
  body {
    font-family: "Poppins", sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
  }
  
  
  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    height: 100vh;
    width: var(--sidebar-width);
    background-color: var(--card-color);
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 20px 0;
    border-right: 1px solid #333;
    z-index: 100;
  }
  .sidebar-logo {
    font-size: 2.5rem;
    color: var(--accent-color);
    margin-bottom: 40px;
  }
  .sidebar-menu {
    list-style-type: none;
    width: 100%;
  }
  .sidebar-menu li {
    width: 100%;
    margin-bottom: 15px;
  }
  .sidebar-menu li a {
    display: flex;
    justify-content: center;
    align-items: center;
    color: var(--subtle-text-color);
    font-size: 1.8rem;
    height: 50px;
    position: relative;
    transition: color 0.3s ease;
  }
  .sidebar-menu li a::before {
    content: "";
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    height: 0;
    width: 5px;
    background-color: var(--accent-color);
    border-radius: 0 5px 5px 0;
    transition: height 0.3s ease;
  }
  .sidebar-menu li a:hover,
  .sidebar-menu li.active a {
    color: var(--accent-color);
  }
  .sidebar-menu li.active a::before {
    height: 80%;
  }
  
  
  .main-content {
    margin-left: var(--sidebar-width);
    padding: 30px 40px;
  }
  h1,
  h2,
  h3 {
    font-weight: 600;
  }
  .header {
    margin-bottom: 30px;
  }
  .header h1 {
    font-size: 2.5rem;
  }
  .header p {
    color: var(--subtle-text-color);
    font-size: 1rem;
  }
  
  
  .card {
    background-color: var(--card-color);
    border-radius: var(--border-radius);
    padding: 25px;
    box-shadow: 0 4px 15px var(--shadow-color);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
  }
  .card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px var(--shadow-color);
  }
  .grid-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 25px;
  }
  
  .card-stat h3 {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.1rem;
    font-weight: 500;
    color: var(--subtle-text-color);
    margin-bottom: 15px;
  }
  .card-stat .stat-number {
    font-size: 3rem;
    font-weight: 700;
    color: var(--accent-color);
    line-height: 1;
  }
  .card-stat p {
    font-size: 1.2rem;
    font-weight: 600;
  }
  .card-stat .stat-date {
    font-size: 1rem;
    font-weight: 400;
    color: var(--subtle-text-color);
  }
  
  
  
  @media (min-width: 992px) {
    .home-masonry {
      display: grid;
      grid-template-columns: repeat(2, 1fr);
      gap: 25px;
    }
  }
  
  #motivational-quote-card {
    grid-column: 1 / -1; 
    text-align: center;
    padding: 40px 20px;
    background: linear-gradient(135deg, #2a2e33, #2f343a);
  }
  #motivational-quote {
    font-size: 2.2rem;
    font-weight: 300;
    line-height: 1.4;
    color: var(--text-color);
    opacity: 0;
    animation: fadeIn 1.5s 0.2s forwards;
    text-shadow: 0 0 15px rgba(107, 243, 215, 0.3);
  }
  @keyframes fadeIn {
    to {
      opacity: 1;
    }
  }
  
  
  
  .subject-card {
    padding: 30px;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
  }
  .subject-card h3 {
    font-size: 1.3rem;
    margin-bottom: 8px;
    font-weight: 500;
  }
  .subject-card .code {
    color: var(--subtle-text-color);
    margin-bottom: 20px;
    font-size: 0.9rem;
  }
  .subject-card .grade {
    align-self: flex-end;
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--accent-color);
    line-height: 1;
  }
  
  
  
  .todo-layout {
    display: flex;
    gap: 30px;
  }
  .active-tasks,
  .completed-tasks {
    flex: 1;
    min-width: 0;
  }
  .active-tasks h2,
  .completed-tasks h2 {
    margin-bottom: 15px;
    font-size: 1.2rem;
    color: var(--subtle-text-color);
  }
  .completed-tasks {
    display: none;
  } 
  @media (min-width: 992px) {
    .completed-tasks {
      display: block;
    }
  }
  
  
  #task-input {
    flex-grow: 1;
    padding: 15px;
    border-radius: var(--border-radius);
    border: none;
    background-color: #33373d;
    color: var(--text-color);
    font-size: 1rem;
  }
  .btn {
    padding: 15px 30px;
    border-radius: var(--border-radius);
    border: none;
    background-color: var(--accent-color);
    color: #111;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.3s ease;
    white-space: nowrap;
  }
  .btn:hover {
    background-color: #55dcb9;
  }
  #active-task-list,
  #completed-task-list-container {
    list-style: none;
  }
  .task-item {
    display: flex;
    align-items: center;
    padding: 15px;
    margin-bottom: 15px;
    transition: background-color 0.3s, opacity 0.4s;
  }
  .task-item span {
    flex-grow: 1;
  }
  .task-item.completed span {
    text-decoration: line-through;
    color: var(--subtle-text-color);
  }
  .task-actions button {
    background: none;
    border: none;
    color: var(--subtle-text-color);
    font-size: 1.5rem;
    cursor: pointer;
    margin-left: 10px;
    transition: color 0.3s ease;
  }
  .task-actions button:hover {
    color: var(--accent-color);
  }
  
  @keyframes moveOut {
    0% {
      opacity: 1;
      transform: translateX(0);
    }
    100% {
      opacity: 0;
      transform: translateX(50px);
    }
  }
  .task-item.moving-out {
    animation: moveOut 0.4s forwards ease-in-out;
  }
  
  
  @media (max-width: 991px) {
    .todo-layout {
      flex-direction: column;
    }
    #add-task-form {
      display: flex;
      gap: 10px;
      margin-bottom: 25px;
    }
    #completed-task-list-container {
      margin-top: 40px;
    }
  }
  
  
  
  #calendar-container {
    padding: 0;
  }
  .calendar-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 25px;
  }
  #month-year {
    font-size: 1.5rem;
  }
  #calendar-nav button {
    background: none;
    border: none;
    color: var(--text-color);
    font-size: 2rem;
    cursor: pointer;
    transition: color 0.3s;
  }
  #calendar-nav button:hover {
    color: var(--accent-color);
  }
  .calendar-grid {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 1px;
    background-color: #333;
  }
  .calendar-day-header {
    background-color: var(--bg-color);
    padding: 10px;
    text-align: center;
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--subtle-text-color);
  }
  .calendar-day {
    background-color: var(--card-color);
    aspect-ratio: 1/1;
    padding: 8px;
    text-align: left;
    cursor: pointer;
    transition: background-color 0.3s;
    position: relative;
  }
  .calendar-day:hover {
    background-color: #3a3f45;
  }
  .calendar-day.other-month {
    color: #555;
    background-color: #24272b;
    cursor: default;
  }
  .calendar-day.today .day-number {
    background-color: var(--accent-color);
    color: var(--bg-color);
    border-radius: 50%;
    width: 28px;
    height: 28px;
    display: inline-flex;
    justify-content: center;
    align-items: center;
  }
  .event-dot {
    position: absolute;
    bottom: 8px;
    left: 8px;
    width: 6px;
    height: 6px;
    background-color: #f26b6b;
    border-radius: 50%;
  }
  
  
  .modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.7);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease, visibility 0s 0.3s linear;
  }
  .modal-overlay.active {
    opacity: 1;
    visibility: visible;
    transition-delay: 0s;
  }
  .modal-content {
    background: var(--card-color);
    padding: 30px;
    border-radius: var(--border-radius);
    width: 90%;
    max-width: 450px;
    position: relative;
    transform: scale(0.95);
    transition: transform 0.3s ease;
  }
  .modal-overlay.active .modal-content {
    transform: scale(1);
  }
  .modal-close {
    position: absolute;
    top: 15px;
    right: 15px;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--subtle-text-color);
  }
  #event-form input {
    width: 100%;
    padding: 12px;
    margin-bottom: 15px;
    border-radius: 10px;
    border: none;
    background-color: #33373d;
    color: var(--text-color);
    font-size: 1rem;
  }
  .event-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 10px;
    padding-bottom: 10px;
    border-bottom: 1px solid #333;
  }
  .event-item:last-child {
    border-bottom: none;
  }
  
  .event-item .delete-event-btn {
    background: none;
    border: none;
    color: var(--subtle-text-color);
    font-size: 1.2rem;
    cursor: pointer;
    transition: color 0.3s ease;
    padding: 5px;
  }
  .event-item .delete-event-btn:hover {
    color: #f26b6b;
  }
  
  
  @media (max-width: 767px) {
    .calendar-day-header {
      font-size: 0.75rem;
      padding: 8px 0;
    }
    .calendar-day {
      padding: 5px;
      font-size: 0.8rem;
    }
    .calendar-day.today .day-number {
      width: 24px;
      height: 24px;
    }
  }
  
  
  
  #timer-container {
    max-width: 450px;
    margin: 40px auto;
    text-align: center;
    position: relative;
  }
  .timer-modes {
    display: flex;
    justify-content: center;
    gap: 10px;
    margin-bottom: 30px;
  }
  .timer-modes button {
    background: none;
    border: 1px solid var(--subtle-text-color);
    color: var(--subtle-text-color);
    padding: 8px 18px;
    border-radius: 20px;
    cursor: pointer;
    transition: all 0.3s ease;
  }
  .timer-modes button.active {
    background-color: var(--accent-color);
    border-color: var(--accent-color);
    color: var(--bg-color);
    font-weight: 600;
  }
  #time-display {
    font-size: 8rem;
    font-weight: 700;
    line-height: 1;
    margin-bottom: 10px;
    color: var(--text-color);
  }
  #session-info {
    color: var(--subtle-text-color);
    margin-bottom: 25px;
    height: 1.2rem;
    font-size: 1.1rem;
  }
  .timer-controls {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 20px;
  }
  #start-pause-btn {
    font-size: 1.2rem;
    padding: 15px 50px;
  }
  #reset-btn {
    background: none;
    border: none;
    color: var(--subtle-text-color);
    font-size: 2rem;
    cursor: pointer;
    transition: color 0.3s, transform 0.3s;
  }
  #reset-btn:hover {
    color: var(--text-color);
    transform: rotate(90deg);
  }
  
  
  .timer-settings-toggle {
    background: none;
    border: none;
    color: var(--subtle-text-color);
    font-size: 1.5rem;
    cursor: pointer;
    position: absolute;
    top: 20px;
    right: 20px;
    transition: color 0.3s;
  }
  .timer-settings-toggle:hover {
    color: var(--accent-color);
  }
  .timer-settings-panel {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.5s ease-in-out, margin-top 0.5s ease-in-out;
    margin-top: 0;
  }
  .timer-settings-panel.open {
    max-height: 300px;
    margin-top: 30px;
  }
  .settings-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 15px;
    text-align: center;
  }
  .settings-grid label {
    display: block;
    margin-bottom: 8px;
    font-size: 0.9rem;
  }
  .settings-grid input {
    width: 80%;
    padding: 8px;
    text-align: center;
    background: #33373d;
    border: none;
    border-radius: 8px;
    color: var(--text-color);
    font-size: 1.1rem;
  }
  
  input[type="number"]::-webkit-inner-spin-button,
  input[type="number"]::-webkit-outer-spin-button {
    -webkit-appearance: none;
    margin: 0;
  }
  input[type="number"] {
    -moz-appearance: textfield;
  }
  
  .page-footer {
    margin-top: 60px;
    padding-top: 30px;
    text-align: center;
    border-top: 1px solid #333;
  }
  
  .page-footer a {
    color: var(--subtle-text-color);
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    font-size: 1rem;
    transition: color 0.3s ease;
  }
  
  .page-footer a:hover {
    color: var(--accent-color);
  }
  
  .page-footer i {
    font-size: 1.5rem;
  }
  
  
  @media (max-width: 768px) {
    .sidebar {
      width: 100%;
      height: 70px;
      flex-direction: row;
      justify-content: space-around;
      bottom: 0;
      top: auto;
      border-top: 1px solid #333;
      border-right: none;
    }
    .sidebar-logo {
      display: none;
    }
    .sidebar-menu {
      display: flex;
      justify-content: space-around;
      height: 100%;
      width: 100%;
    }
    .sidebar-menu li {
      margin-bottom: 0;
      flex-grow: 1;
    }
    .sidebar-menu li a::before {
      top: 0;
      left: 50%;
      transform: translateX(-50%);
      width: 40%;
      height: 4px;
      border-radius: 0 0 5px 5px;
    }
    .sidebar-menu li.active a::before {
      height: 4px;
    }
    .main-content {
      margin-left: 0;
      padding: 20px 20px 90px 20px;
    }
    .header h1 {
      font-size: 2rem;
    }
    .grid-container,
    .home-masonry {
      grid-template-columns: 1fr;
    }
    #motivational-quote {
      font-size: 1.5rem;
    }
    #time-display {
      font-size: 5rem;
    }
  }