:root {
    --bg-color: #f0f0f0;
    --text-color: #333;
    --primary-color: #4a90e2;
    --secondary-color: #e74c3c;
    --accent-color: #2ecc71;
}

.dark-mode {
    --bg-color: #222;
    --text-color: #f0f0f0;
    --primary-color: #3a7bd5;
    --secondary-color: #c0392b;
    --accent-color: #27ae60;
}

body {
    font-family: 'Roboto', sans-serif;
    max-width: 800px;
    margin: 0 auto;
    padding: 20px;
    background-color: var(--bg-color);
    color: var(--text-color);
    transition: background-color 0.3s, color 0.3s;
}

h1, h2 {
    font-family: 'Montserrat', sans-serif;
    color: var(--primary-color);
}

.timer-display {
    font-size: 4em;
    margin: 20px 0;
    font-weight: 300;
    color: var(--secondary-color);
}

button {
    margin-right: 10px;
    padding: 10px 20px;
    font-size: 1em;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s;
}

button:hover {
    background-color: var(--secondary-color);
}

ul {
    list-style-type: none;
    padding: 0;
}

li {
    margin-bottom: 10px;
    padding: 10px;
    background-color: rgba(255, 255, 255, 0.1);
    border-radius: 5px;
}

input[type="text"], input[type="number"] {
    padding: 5px;
    font-size: 1em;
    border: 1px solid var(--primary-color);
    border-radius: 3px;
    background-color: var(--bg-color);
    color: var(--text-color);
}

#darkModeToggle {
    position: fixed;
    top: 20px;
    right: 20px;
    background-color: var(--accent-color);
}

.remove-task {
    background-color: var(--secondary-color);
    color: white;
    border: none;
    border-radius: 3px;
    padding: 2px 5px;
    margin-left: 10px;
    cursor: pointer;
    display: none;
}

li.completed .remove-task {
    display: inline-block;
}

.tag {
    display: inline-block;
    padding: 2px 5px;
    margin-right: 5px;
    background-color: var(--accent-color);
    color: white;
    border-radius: 3px;
    font-size: 0.8em;
}

#customIntervals {
    display: flex;
    gap: 10px;
    margin-bottom: 10px;
}

#customIntervals input {
    width: 50px;
}

#breakSuggestion {
    margin-top: 10px;
    font-style: italic;
}

.kanban-board {
    display: flex;
    justify-content: space-between;
    margin-top: 20px;
}

.kanban-column {
    flex: 1;
    margin: 0 10px;
    padding: 10px;
    background-color: rgba(255, 255, 255, 0.1);
    border-radius: 5px;
}

.kanban-column h3 {
    text-align: center;
}

.heat-map {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 2px;
    margin-top: 20px;
}

.heat-map-cell {
    width: 20px;
    height: 20px;
    background-color: var(--accent-color);
    opacity: 0.2;
}