Physics puzzle games are one of the simplest types of game around, yet they manage to remain compelling to players. Overcoming new obstacles and experimenting with new tools to complete the challenges will likely continue to draw an audience for a long time coming. Now, mobile app developer Estelion is bringing one of its titles, Ratventure Challenge, to Steam on May 8th.

The game is a take on the bridge-builder type of physics puzzler, challenging players to create a structure to support the two rats to collect cheese across pits and perils. A limited hint system is available, as is the option to undo the last placed piece. Each level is graded on a scale of one to three stars for the time it takes to complete the puzzle as well as how many pieces used. Unfortunately, this ties in to one of the most disappointing elements of this game, in that it has trappings of its roots as a mobile game intact - it features microtransactions to purchase more moves on a level. These feel rather overpriced, and keeping them could definitely leave players feeling wary.

The levels themselves offer a good amount of variety and challenge, and it is enjoyable to learn how the physics affects the construction as the bridge (or tower in some more vertically-oriented levels) grows in size. In a very interesting design decision, the game is not completely separated into building and running segments. Rather, the player is able to move their rats along the bridge, then return to place more. Managing the rats' weight in addition to the pieces and obstacles is the most engaging part of the game play, and a welcome change to the standard formula.

Ratventure Challenge looks pleasant, with its gentle colour palette and cartoonish 2D aesthetic. There's not a lot of animation to the sprites, but the bridge wobbles and sways as weight is applied to it in a satisfying way. Players will see the results of their decisions as they happen and can try and correct as their construction veers close to toppling or coming into contact with a dangerous obstacle. Sound is minimal at best, with some ambient background music playing in the levels and not much else. The music itself is simple but repetitive, and since each set of twelve levels uses the same music, it gets a little old quickly.

The biggest complaints I can make about the game all seem to tie back into its origins as a mobile game. Besides the microtransactions themselves, which are a nuisance, but not required to play, there is the undo function which is restricted to only the last piece placed. This means that often it's too late to fix, and the player's only recourse is to restart the entire level, or if they are so inclined, purchase a few extra moves to finish. The motivation to buy moves in this situation is enhanced by the restart level button being tucked away in the menu while the purchase button is clearly on screen during play.

Still, microtransactions aside, the game is fun and challenging. It introduces new obstacles such as heavy creatures (or perhaps they're rocks with eyes and hair) which will hop on to the bridge if a piece is close enough, altering the weight distribution, and buzzsaws which will destroy placed pieces (or the unfortunate rats) as players progress. Also adding to the challenge are pieces like swinging ropes and unanchored bridge parts which require new thinking to use effectively as they come up in play. These added elements work to keep the game fresh and engaging, and keep ramping up the challenge as the player becomes familiar with elements they've been working with already.

Anybody who is interested in physics puzzlers should consider Ratventure Challenge, as well as folks who are looking for a simple but engaging challenge. While not a gem of the genre, it offers up enough variety and interesting mechanics to keep players going for a while.