* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: Arial, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
}

.container {
    max-width: 600px;
    margin: 0 auto;
    background: white;
    border-radius: 20px;
    padding: 30px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
}

h1 {
    text-align: center;
    margin-bottom: 30px;
    color: #333;
}

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

.timer-display {
    margin: 30px 0;
}

.time-circle {
    position: relative;
    display: inline-block;
}

.progress-ring-circle {
    transition: stroke-dashoffset 1s linear;
    transform: rotate(-90deg);
    transform-origin: 50% 50%;
}

.time-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 3em;
    font-weight: bold;
    color: #333;
}

.timer-controls {
    margin: 20px 0;
}

.timer-controls button {
    padding: 12px 24px;
    margin: 0 10px;
    border: none;
    border-radius: 25px;
    font-size: 16px;
    cursor: pointer;
    transition: all 0.3s;
}

#start-btn {
    background: #4caf50;
    color: white;
}

#pause-btn {
    background: #ff9800;
    color: white;
}

#reset-btn {
    background: #f44336;
    color: white;
}

.timer-controls button:disabled {
    background: #ccc;
    cursor: not-allowed;
}

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

.mode-btn {
    padding: 10px 15px;
    border: 2px solid #e0e0e0;
    background: white;
    border-radius: 20px;
    cursor: pointer;
    transition: all 0.3s;
}

.mode-btn.active {
    background: #4caf50;
    color: white;
    border-color: #4caf50;
}

.tasks-section, .session-history {
    margin-top: 30px;
    padding: 20px;
    background: #f8f9fa;
    border-radius: 10px;
}

#task-form {
    display: flex;
    gap: 10px;
    margin-bottom: 15px;
}

#task-input {
    flex: 1;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 5px;
}

#task-form button {
    padding: 10px 20px;
    background: #007bff;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
}

#task-list, #history-list {
    list-style: none;
}

.task-item, .history-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px;
    margin-bottom: 8px;
    background: white;
    border-radius: 5px;
    border-left: 4px solid #007bff;
}

.task-item.completed {
    opacity: 0.6;
    text-decoration: line-through;
}

.delete-btn {
    background: #dc3545;
    color: white;
    border: none;
    padding: 5px 10px;
    border-radius: 3px;
    cursor: pointer;
}