South Korea. It uses free-to-play elements and involves players trying to collect pets that are trapped inside blocks. Common elements The Mr. Driller games are puzzle action games and have been described as a cross between Puyo Puyo and Dig Dug. Players control a character that must destroy, or "drill", colorful formations of blocks in order to reach the bottom of a well. Blocks of the same color can connect to each other; if four of a kind connect, they are destroyed, which can be used to create chain reactions. The player has a constantly depleting oxygen meter that can be replenished by collecting blue air capsules. Oxygen is lost by destroying brown "x"-marked blocks, which take five hits to destroy. Certain characters have their own attributes and abilities, such as depleting oxygen less and moving faster. Later games introduce mechanics such as star-marked blocks that disappear after a brief period, boss fights, power-ups, and game modes that implement ideas from role-playing games. Development The original Mr. Driller was created by R4: Ridge Racer Type 4 director Yasuhito Nagaoka and former Tecmo employee Hideo Yoshizawa. Nagaoka drafted the game in 1998 as a second sequel to Dig Dug, a classic Namco arcade game from 1982, aptly named Dig Dug 3. The game was designed to be more puzzle-like in gameplay structure, a contrast to the action-oriented gameplay of Dig Dug and Dig Dug II. Yoshizawa made several alterations to Nagaoka's prototype build, including the renaming to Mr. Driller. Namco released the game in arcades in 1999 to critical and commercial success. Mr. Driller was ported to several platforms, including the Dreamcast, PlayStation, and Game Boy Color. Yoshizawa and Nagaoka quickly began work on a sequel, Mr. Driller 2, in late 1999. The two worked to implement new features, such as a second-player character and making the gameplay faster and more chaotic than the original. The sequel was released for arcades in 2000 to moderate success and was followed by a port for the Game Boy Advance in 2001. The Game Boy Advance version was a launch title for the system and sold over 100,000 copies, however, the game wasn't released in North America and Europe until 2005. The third entry, Mr. Driller G, was released in 2001 for arcades and later the PlayStation. The game was created to be more story-driven than the previous installments, which expanded on the Mr.