
The Gungrounds team grew over time, adding programmers Ivan Gabriel Juričić and Goran Tomašić, as well as artist Ana Marija Lončar, who the team met at Reboot InfoGamer 2018. While exhibiting Spitfire Inferno at the Reboot InfoGamer conference in Croatia, it was acknowledged by members of Croteam, who tracked the team's progress across further events-Reboot Develop, the Slovenian Games Conference, and the Central European Games Conference-and eventually invited them to Croteam's business incubator programme. They had previously collaborated on a game for the "Indies VS PewDiePie" game jam held in November 2014. Kristian Macanga and Guy Unger initially developed a game titled Spitfire or Spitfire Inferno, which they modelled after Geometry Wars. It was the studio's second game after Rocking Pilot, which was co-developed and published by Mad Head Games in May 2017. Serious Sam: Tormental was developed by Gungrounds, a Croatian indie game studio. The game can be played cooperatively with a second local player. After the vault, the stages loop and the player returns to the first stage with an increased difficulty. These power-ups become permanently available to find during regular gameplay. Over time, the player collects thirty-two black keys used to unlock power-ups in the vault that occurs after completing all stages once. When the player character's health is depleted, gameplay pauses and the player is reset to the start of the game with all weapons and upgrades revoked. Each character has a unique special ability, such as Sam, who can jump over hazards.

Between rooms, characters can be freed using previously collected golden keys to make them selectable at the start of the game. The player can also activate bombs placed in rooms, which inflict damage on both the character and enemies. Large enemies with low health may be defeated with such a roll, which grants better rewards than a regular kill. To evade enemies and projectiles, the player character can perform a dodge roll. Upgrades include bullets that ignite enemies and a rate of fire increase in exchange for a lowered damage per bullet. Chests provide three random upgrades to choose from, while shops require the spending of the currency obtained by defeating enemies. The primary weapon can be enhanced through "mods" either found in chests or purchased at shops that appear within stages. The character can simultaneously use two weapons: a primary weapon with highly available ammunition and a "serious" weapon with high power and limited bullets. These enemies use either melee or projectiles, both of which inflict damage on the player character. Each room contains enemies that need to be defeated before the player can progress. They traverse procedurally generated rooms within multiple thematic stages. The player chooses from one of several player characters, starting with Sam "Serious" Stone and unlocking further characters during gameplay. Mental's frontal lobe serves as a hub area. It takes place within the mind of Mental, the antagonist of the Serious Sam series. Serious Sam: Tormental is a top-down shooter with rogue-lite elements. The player, as NETRICSA (centre), fighting several enemies The game received mixed reviews, with praise for its humour, art, and combat, with criticism towards technical issues, repetitiveness, and lack of innovation. It was made available in early access in April 2019 and released in April 2022.

Spitfire Inferno was renamed Tormental, then Serious Sam: Tormental. After exhibiting the game at several video game conferences, the studio became a part of Croteam Incubator, the development team expanded, and the game's theme was shifted to the Serious Sam series. Gungrounds initially developed Spitfire Inferno with inspiration from Geometry Wars. The stages then loop with increasing difficulty. After completing all stages, the players can use black keys to unlock power-ups from a vault. Upon the player character's defeat, the player is reset to the start of the game. The unlockable player characters can perform dodge rolls and a unique special ability. They use two weapons each, of which the primary weapon can be enhanced through "mods" found throughout the game. One or two players traverse procedurally generated levels across several stages set in the mind of Mental, the antagonist of the Serious Sam series. Serious Sam: Tormental is a 2022 top-down shooter and rogue-lite game developed by Gungrounds and published by Devolver Digital.
