The Espruino Puck.js can also be used as a traditional board through a Web-based IDE hosted on your computer. The microcontroller also uses less power than Linux Boards (although a lot less powerful) so will run longer on battery power.
The casing on the Puck.js is a soft silicone cover with a tactile button mounted inside of a hard ABS plastic backing with perforations for access to the board's pins inside. It also runs from a 3V Lithium coin cell battery (included) which fits snuggly in the casing.
Note: Do not re-fit the PCB upside-down or force it into the case. If positioned correctly it should slide in. Forcing the PCB or fitting it upside-down could damage the aerial which will stop Puck.js's Bluetooth from working correctly.