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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 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: 12px;
    box-shadow: 0 20px 60px rgba(0,0,0,0.3);
    padding: 30px;
}

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

h1 {
    color: #333;
    font-size: 2em;
}

.help-btn {
    background: #ff6b6b;
    color: white;
    padding: 10px 20px;
    border-radius: 20px;
    text-decoration: none;
    font-weight: bold;
    transition: transform 0.2s;
}

.help-btn:hover {
    transform: scale(1.1);
}

.input-section {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

#todoInput {
    flex: 1;
    padding: 15px;
    border: 2px solid #ddd;
    border-radius: 8px;
    font-size: 16px;
}

#todoInput:focus {
    outline: none;
    border-color: #667eea;
}

#addBtn {
    background: #667eea;
    color: white;
    border: none;
    padding: 15px 30px;
    border-radius: 8px;
    font-weight: bold;
    cursor: pointer;
    transition: background 0.3s;
}

#addBtn:hover {
    background: #5568d3;
}

.filter-section {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

.filter-btn {
    flex: 1;
    padding: 10px;
    border: 2px solid #ddd;
    background: white;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s;
}

.filter-btn.active {
    background: #667eea;
    color: white;
    border-color: #667eea;
}

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

.todo-item {
    display: flex;
    align-items: center;
    padding: 15px;
    border: 2px solid #f0f0f0;
    border-radius: 8px;
    margin-bottom: 10px;
    transition: all 0.3s;
}

.todo-item:hover {
    border-color: #667eea;
}

.todo-item.done {
    opacity: 0.6;
}

.todo-item.done .todo-text {
    text-decoration: line-through;
}

.todo-checkbox {
    width: 24px;
    height: 24px;
    margin-right: 15px;
    cursor: pointer;
}

.todo-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.todo-text {
    font-size: 16px;
}

.todo-judgment {
    font-size: 13px;
    color: #999;
    font-style: italic;
    opacity: 0.8;
}

.delete-btn {
    background: #ff6b6b;
    color: white;
    border: none;
    padding: 8px 15px;
    border-radius: 6px;
    cursor: pointer;
    font-weight: bold;
}

.stats {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 20px;
    border-top: 2px solid #f0f0f0;
}

#clearDone {
    background: #ff6b6b;
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 6px;
    cursor: pointer;
    font-weight: bold;
}

/* Mobile responsive */
@media (max-width: 480px) {
    .container {
        padding: 20px;
    }

    h1 {
        font-size: 1.5em;
    }

    .input-section {
        flex-direction: column;
    }

    #addBtn {
        width: 100%;
    }

    .filter-section {
        flex-direction: column;
    }

    .stats {
        flex-direction: column;
        gap: 10px;
        align-items: stretch;
    }

    #clearDone {
        width: 100%;
    }
}