The board is round and has alligator-clip pads around it so you don't have to solder or sew to make it work. You can power it from USB, a AAA battery pack, or with a Lipoly battery (for advanced users). Circuit Playground Express has built-in USB support. Built in USB means you plug it in to program it and it just shows up, no special cable or adapter required. Just program your code into the board then take it on the go! Here's some of the great goodies baked in to each Circuit Playground Express:
10 x mini NeoPixels, each one can display any color
1 x Motion sensor (LIS3DH triple-axis accelerometer with tap detection, free-fall detection)
1 x Temperature sensor (thermistor)
1 x Light sensor (phototransistor). Can also act as a color sensor and pulse sensor.
1 x Sound sensor (MEMS microphone)
1 x Mini speaker with class D amplifier (7.5mm magnetic speaker/buzzer)
2 x Push buttons, labeled A and B
1 x Slide switch
Infrared receiver and transmitter - can receive and transmit any remote control codes, as well as send messages between Circuit Playground Expresses. Can also act as a proximity sensor.
8 x alligator-clip friendly input/output pins
Includes I2C, UART, 8 pins that can do analog inputs, multiple PWM output
7 pads can act as capacitive touch inputs and the 1 remaining is a true analog output
Green "ON" LED so you know its powered
Red "#13" LED for basic blinking
ATSAMD21 ARM Cortex M0 Processor, running at 3.3V and 48MHz
2 MB of SPI Flash storage, used primarily with CircuitPython to store code and libraries.
MicroUSB port for programming and debugging
USB port can act like serial port, keyboard, mouse, joystick or MIDI!