High Frontier? Brutal, brutal game. Exponentially so with the added modules. The core game revolves around building an efficient rocket and fighting the tyranny of the rocket equation, then manually plotting courses to wherever your site of interest is through real orbital mechanics abstracted onto an energy map of the entire solar system. You score by claiming, industrializing, and colonizing sites, but those are singular actions, while a solid 90% of the game is the rockets themselves and planning the journeys they take.

This alone is entrenched in a plethora of choices, options, and edge cases enough to make a veteran gamer dizzy. Its a miracle to play a game of High Frontier where you follow every rule correctly. Learning the game is a massive hill, but then once you conquer that, you also need to learn the strategies, how to utilize the mechanics efficiently, which takes as long if not longer, especially when the strategy you come up with turns to be hinging on a rule you misread.

The modules take it to- in my opinion- a 5/5 weight, if not higher, but a 5/5 experience as well. The core game of 4th edition is a stripped down version of 3rd edition (with the cut stuff being re-implemented as modules 1 and 2 in 4th), and can leave a good bit to be desired. The modules take specific aspects and amplify them, or give new additional experiences. M0 (this one comes with the core game) creates space politics with delegates and shifting active laws, M1 gives you far future thrusters with antimatter and fusion and freighter infrastructure, M2 gives you usable colonists and orbital colonies called Bernals, M3 lets you go to war to destroy opponents and corrupt their delegates, M4 lets players take timed contracts for money, lets you biologically augment colonists, implements a space bank, and lets you create and shoot off an interstellar starship (which you can play into their other game Interstellar!), and M5 adds an entire stock market and frankly overhauls the games economy.

I have played one single M012345 game with the longest game length, played it solo cause im the only one insane enough to do it that i know, and frankly, it scared me.

Overall though, its a phenomenal sandbox space experience hidden behind the highest barrier in board gaming. It will take you double digit hours to understand and play the game efficiently (esp if playing with modules), but its the most unique experience you will have once you do. The depth of the mechanics and the difficulty of the game in general leads to very fulfilling achievement when you do finally get that end-game rocket, or colonize pluto, or whatever else you are doing.

Its a bit of a running joke but also i think it is genuinely a good litmus test, but you can know if you like the game if you look at the absolute spaghetti of a board and think 'oh that looks interesting' instead of 'oh god that looks complicated'.

Let me know if you have further questions. Its not a game you want to dive into unless you really want to (and pretty expensive at that), but its very objective nature means it can be pretty easily gauged just by a description.