:root {
    --primary-color: #e74c3c;
    --secondary-color: #2c3e50;
    --accent-color: #3498db;
    --light-color: #ecf0f1;
    --dark-color: #2c3e50;
    --background-color: #ffffff;
    --text-color: #333333;
    --shadow-color: rgba(0, 0, 0, 0.1);
    --border-color: #ddd;
}

.dark-mode {
    --primary-color: #e74c3c;
    --secondary-color: #34495e;
    --accent-color: #3498db;
    --light-color: #2c3e50;
    --dark-color: #ecf0f1;
    --background-color: #1a1a1a;
    --text-color: #f5f5f5;
    --shadow-color: rgba(0, 0, 0, 0.3);
    --border-color: #444;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    transition: background-color 0.3s, color 0.3s;
}

body {
    background-color: var(--background-color);
    color: var(--text-color);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    width: 100%;
    max-width: 1000px;
    background-color: var(--background-color);
    border-radius: 15px;
    box-shadow: 0 10px 30px var(--shadow-color);
    overflow: hidden;
    padding: 20px;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
}

h1,
h2 {
    color: var(--primary-color);
}

.mode-toggle {
    display: flex;
    align-items: center;
    gap: 10px;
}

.switch {
    position: relative;
    display: inline-block;
    width: 60px;
    height: 30px;
}

.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--secondary-color);
    transition: .4s;
    border-radius: 34px;
}

.slider:before {
    position: absolute;
    content: "";
    height: 22px;
    width: 22px;
    left: 4px;
    bottom: 4px;
    background-color: var(--light-color);
    transition: .4s;
    border-radius: 50%;
}

input:checked+.slider {
    background-color: var(--accent-color);
}

input:checked+.slider:before {
    transform: translateX(30px);
}

.timer-container {
    text-align: center;
    margin-bottom: 30px;
}

.mode-selector {
    display: flex;
    justify-content: center;
    margin-bottom: 20px;
    gap: 10px;
}

.mode-btn {
    padding: 10px 20px;
    border: none;
    border-radius: 25px;
    background-color: var(--light-color);
    color: var(--text-color);
    cursor: pointer;
    font-weight: bold;
    transition: all 0.3s;
}

.mode-btn.active {
    background-color: var(--primary-color);
    color: white;
}

.mode-btn:hover:not(.active) {
    background-color: var(--border-color);
}

.timer-display {
    font-size: 6rem;
    font-weight: bold;
    margin: 20px 0;
    color: var(--primary-color);
    font-family: 'Courier New', monospace;
}

.timer-controls {
    display: flex;
    justify-content: center;
    gap: 15px;
    margin-top: 20px;
}

.control-btn {
    padding: 12px 25px;
    border: none;
    border-radius: 5px;
    background-color: var(--accent-color);
    color: white;
    font-size: 1rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    transition: all 0.3s;
}

.control-btn:hover {
    background-color: var(--secondary-color);
    transform: translateY(-2px);
}

.control-btn:disabled {
    background-color: var(--border-color);
    cursor: not-allowed;
    transform: none;
}

.settings-panel,
.task-manager {
    background-color: var(--light-color);
    padding: 20px;
    border-radius: 10px;
    margin-bottom: 20px;
}

.setting {
    margin-bottom: 15px;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.setting label {
    margin-right: 10px;
    font-weight: 500;
}

.setting input[type="number"] {
    width: 70px;
    padding: 8px;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    background-color: var(--background-color);
    color: var(--text-color);
}

.setting input[type="checkbox"] {
    transform: scale(1.3);
}

.setting select {
    padding: 8px;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    background-color: var(--background-color);
    color: var(--text-color);
}

.save-btn {
    width: 100%;
    padding: 12px;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 5px;
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.3s;
}

.save-btn:hover {
    background-color: #c0392b;
    transform: translateY(-2px);
}

.task-input {
    display: flex;
    gap: 10px;
    margin-bottom: 15px;
}

.task-input input {
    flex: 1;
    padding: 10px;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    background-color: var(--background-color);
    color: var(--text-color);
}

.task-input button {
    padding: 10px 15px;
    background-color: var(--accent-color);
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
    transition: all 0.3s;
}

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

#task-list {
    list-style: none;
    margin-bottom: 20px;
}

.task-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px;
    background-color: var(--background-color);
    border-radius: 5px;
    margin-bottom: 8px;
    border-left: 4px solid var(--primary-color);
}

.task-item.completed {
    opacity: 0.7;
    border-left-color: #2ecc71;
}

.task-item.completed .task-text {
    text-decoration: line-through;
}

.task-actions {
    display: flex;
    gap: 10px;
}

.task-actions button {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-color);
    font-size: 1rem;
    transition: all 0.2s;
}

.task-actions button:hover {
    transform: scale(1.2);
}

.task-actions .complete-btn:hover {
    color: #2ecc71;
}

.task-actions .delete-btn:hover {
    color: #e74c3c;
}

.task-stats {
    text-align: right;
    font-style: italic;
    color: var(--primary-color);
}

@media (max-width: 768px) {
    .timer-display {
        font-size: 4rem;
    }

    .container {
        padding: 15px;
    }

    .mode-selector {
        flex-direction: column;
        align-items: center;
    }

    .timer-controls {
        flex-direction: column;
        align-items: center;
    }

    .control-btn {
        width: 100%;
        justify-content: center;
    }
}