The GA-2100 earned the nickname CasiOak for an octagonal bezel that shares its design language with the Audemars Piguet Royal Oak, and the GA-2100K-5A gives that platform a nightlife design treatment. The amber-brown translucent case and matte resin strap pair with a glossy black dial and red neon accents, a combination Casio designed to evoke laser strobes and fog machine haze at a music festival. Carbon Core Guard construction keeps it at 51 grams while maintaining 200 meters of water resistance, and the analog-digital display runs dual Super Illuminator LEDs, world time across 31 time zones, a 1/100-second stopwatch, five daily alarms, and a hand shift function that clears the analog hands for an unobstructed view of the digital display.