Reading your recent posts has been like dipping my bottom over and over into a bath of the silkiest oils and creams.
Steam Tunnel is one of a line of zip-lock games called Hip Pocket Games (a tiny little division of Cheapass Games). Games in this line usually have little more than a small deck of cards -- but they indeed can fit in your hip pocket, and are some of the cheapest of the cheap Cheapass games. Liking the idea (and the price) I bought a number of them a few years ago, before I got into the gaming hobby in any big way. Lately I've had a desire to revisit them, and for this game, at least, I will post a review.
The game comes with fold-out instructions and a deck of (business card style) cards; you will need to provide a dozen or so markers per player. Each card depicts multiple tunnels connecting different sides. 32 of these cards are placed face-down along with 4 face-up cards featuring tunnel ends worth various numbers of points. These are set up in a 6 x 6 pattern.
On a player's turn, he must flip over one of the face-down cards and reveal the tunnels underneath. He cannot choose the orientation of the card. He is then allowed to place a marker on any unoccupied segment of incomplete tunnel on any face-up card. Alternatively, he may place a marker on a face-down card to "bury" it and keep it from being flipped; tunnels are assumed to go straight through them.
When a player flips over the last face-down card (that is not buried), the game immediately ends. For each complete tunnel, the player with the most markers in it scores points equal to the number of face-up segments (buried cards won't score) multiplied by the sum of the values at the ends. The ends depicted on the 4 face-up cards at the start are valued 2 through 4, while some black ends on the face-down cards are worth zero. So, if a tunnel doesn't have at least one end worth points, it doesn't matter how long the tunnel is, it will be worth zero points.
As you may guess from the above description, the game requires a great deal of luck to win. If you place markers on a tunnel that later becomes quite long, it will either be worth a ridiculously high number of points, or none at all. There is no strategy you can effect so that particular tunnels will become longer, and no real ability to tactically decide which tunnels you should compete for ownership.
If a tunnel becomes ridiculously long due to forks, as one does in the preceding photo, then the score from this one tunnel could be much higher than all the other tunnels combined. Forks not only make tunnels longer, but the multiplier may be larger as well since there are more endpoints. Once it is clear that a tunnel may become so long, it is in players' best interests to compete for ownership in just this one tunnel; players may just go back and forth, tit-for-tat until the tunnel is closed and a winner of the tunnel (and then, possibly, the game) can be determined. This focus on a single tunnel detracts from the rest of the game.
To address this, I would recommend that you remove tunnel forks from the deck, a variant included in the game rules. Though long tunnels are certainly still possible, their scores tend not to become ridiculous.
There are few decisions to make in Steam Tunnel. You choose which card to flip face-up, but the possible results are so varied that it's impossible to know whether flipping a particular card will be a good decision. You choose which tunnels to place markers on, but this decision is usually either a shot in the dark or plainly obvious.
I do still enjoy the game somewhat. It is quick and the rules are very simple. It is perhaps best to approach it as a betting game, placing markers on tunnels while they are short and just hope for the best. The game is very random; ideally multiple rounds would be played to even out the luck, but the game would then be prohibitively long. As-is, it is fairly short (and, of course, cheap), so there may be room for this in your collection as a game to play with children or as a filler.
I agree that luck tends to dominate though there are tactical choices that can make or break tunnels such as not claiming a new tunnel section but rather locking down a card so that your tunnel or someone else's goes straight through that card rather than risking that tunnel being terminated or diverted.
The worst part of this came is the scoring. Tracing tunnels that fork can be annoying especially if they self-intersect. Scoring takes longer than playing cards and tokens. While scoring in Light Speed also takes longer than playing at least you are seeing things blowup while you're doing it.
Another reviewer likens this to Nexus but I think that comparison is not strong. Scoring is much more direct (in Nexus it happens during the game not after), there is no wrap around and by placing a token you will reduce the points for others (if the path is closed) rather than hope that when a closed path is formed it will turn out that you have equal or more tokens on the path.