* { margin: 0; padding: 0; box-sizing: border-box; }
body { font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Arial, sans-serif; background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); min-height: 100vh; display: flex; justify-content: center; align-items: center; padding: 20px; }
.container { background: white; border-radius: 12px; box-shadow: 0 20px 60px rgba(0,0,0,0.3); width: 100%; max-width: 500px; padding: 30px; }
header { text-align: center; margin-bottom: 25px; }
header h1 { color: #333; font-size: 2em; margin-bottom: 8px; }
.credit { display: inline-block; color: #667eea; text-decoration: none; font-size: 0.85em; font-weight: 500; }
.credit:hover { text-decoration: underline; }
.input-section { display: flex; gap: 10px; margin-bottom: 20px; }
#todoInput { flex: 1; padding: 12px 15px; border: 2px solid #e0e0e0; border-radius: 8px; font-size: 1em; transition: border-color 0.3s; }
#todoInput:focus { outline: none; border-color: #667eea; }
#addBtn { padding: 12px 25px; background: #667eea; color: white; border: none; border-radius: 8px; cursor: pointer; font-size: 1em; font-weight: 600; transition: background 0.3s; }
#addBtn:hover { background: #5568d3; }
#todoList { list-style: none; }
.todo-item { background: #f8f9fa; padding: 15px; margin-bottom: 10px; border-radius: 8px; display: flex; align-items: center; gap: 12px; transition: transform 0.2s, box-shadow 0.2s; }
.todo-item:hover { transform: translateY(-2px); box-shadow: 0 4px 12px rgba(0,0,0,0.1); }
.todo-item.completed { opacity: 0.6; }
.todo-item.completed .todo-text { text-decoration: line-through; color: #999; }
.todo-checkbox { width: 20px; height: 20px; cursor: pointer; }
.todo-text { flex: 1; color: #333; font-size: 1em; }
.delete-btn { background: #ff4757; color: white; border: none; padding: 8px 15px; border-radius: 6px; cursor: pointer; font-size: 0.9em; transition: background 0.3s; }
.delete-btn:hover { background: #ee5a6f; }
@media (max-width: 600px) { .container { padding: 20px; } header h1 { font-size: 1.5em; } }