It is a single-panel PCB. Sideboards are broken apart and soldered to the main board with edge pads. To me, it looks much neater compared to bulky headers. Some components were replaced with SMD equivalents. Soldermask was modified as trees were intended to be small Christmas gifts. 

FEATURES

• 2x AAA series connected batteries
• 3.3v running voltage - boosted with IC from batteries voltage
• Atmega328p running on an internal 8MHz clock.
• 12x bicolour LEDs controlled with P-channel MOSFETs and IO pins as sinks.
• Only SMD components for fast reflow oven assembly