More complex Arduino projects can accomplish a wide range of tasks, from automating home appliances to creating interactive art installations. Some examples include:

1. Home automation: Arduino can be used to control lighting systems, air conditioning, and other home appliances. You can program the Arduino to turn on the lights when you enter a room, adjust the temperature based on your preferences, or even set up a smart irrigation system for your garden.

2. Robotics: Arduino is a popular platform for building robots. With the right components and programming, you can create a robot that can navigate, detect obstacles, and perform a variety of tasks.

3. Data logging: Arduino can be used to collect data from sensors and other devices and store it on an SD card or transmit it wirelessly to a computer. This is useful for monitoring environmental conditions, tracking vehicle performance, or analyzing the behavior of industrial machinery.

4. Wearables: Arduino can be used to create wearable technology, such as fitness trackers, smart watches, and even clothing that lights up or changes color in response to external stimuli.

5. Music and sound: Arduino can be used to create musical instruments, sound installations, and other audio-related projects. You can use it to control synthesizers, create MIDI interfaces, or build your own electronic drum kit.

These are just a few examples of the many complex Arduino projects that can be accomplished with some creativity and know-how. The possibilities are virtually endless, and the only limit is your imagination.