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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.card {
    background: white;
    border-radius: 12px;
    padding: 30px;
    box-shadow: 0 10px 40px rgba(0,0,0,0.1);
    max-width: 400px;
    width: 100%;
}

h1 {
    color: #333;
    margin-bottom: 20px;
    text-align: center;
}

.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

input[type="text"],
input[type="password"] {
    width: 100%;
    padding: 12px;
    margin-bottom: 15px;
    border: 2px solid #e0e0e0;
    border-radius: 8px;
    font-size: 14px;
}

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

.btn {
    width: 100%;
    padding: 12px;
    border: none;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s;
}

.btn:hover {
    transform: translateY(-2px);
}

.btn-primary {
    background: #667eea;
    color: white;
}

.btn-logout {
    padding: 6px 12px;
    border: none;
    border-radius: 6px;
    background: #ff4757;
    color: white;
    cursor: pointer;
    font-size: 12px;
}

.text-center {
    text-align: center;
    margin-top: 15px;
    color: #666;
}

.text-center a {
    color: #667eea;
    text-decoration: none;
}

.alert {
    padding: 10px;
    border-radius: 6px;
    margin-bottom: 15px;
    text-align: center;
}

.alert.error {
    background: #fee;
    color: #c33;
}

.alert.success {
    background: #efe;
    color: #3c3;
}

.todo-form {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

.todo-form input {
    flex: 1;
    margin-bottom: 0;
}

.todo-form button {
    width: auto;
    padding: 12px 20px;
}

.todo-list {
    margin-top: 20px;
}

.todo-item {
    display: flex;
    align-items: center;
    padding: 12px;
    border: 2px solid #f0f0f0;
    border-radius: 8px;
    margin-bottom: 10px;
}

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

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

.todo-checkbox {
    width: 20px;
    height: 20px;
    margin-right: 12px;
    cursor: pointer;
}

.todo-text {
    flex: 1;
    color: #333;
}

.todo-delete {
    background: #ff4757;
    color: white;
    border: none;
    padding: 6px 12px;
    border-radius: 6px;
    cursor: pointer;
    font-size: 12px;
}

.todo-delete:hover {
    background: #ee5a6f;
}