It's hard, but not impossible. I did super strength (ladder grab) first, and have completed the game. I would like the ability to reset and plan buying Tenacity first, though, as additional challenge.
adding the ability to choose which "type" your booster packs come from -- necro, lizard/orc, holy, mechanic, bandit, general, etc. -- would be a nice feature.
Ooh -- another idea, borrowed from Through the Ages, a very different card game:
What if cards had two possible gold costs: one if you were paying the extra crystal/iron, and one if you couldn't?
I love the concept, but the implementation has some quirks. Yes, gold is very important. Two suggestions: you could limit strictly the amount of gold mines in a deck, effectively encouraging smaller decks, and preventing people from attempting to stuff their decks with gold mines. That would encourage small deck building to concentrate gold. You could start other resources with a 1/second increase, and make most cards cost other resources to put into play, like the apprentice blacksmiths and archers. Remember, all cards have a reasonably steep gold cost for drawing in the first place. And, for display: every card has some consistent icons, which once you've figured them out, are straightforward, and some special effect. Adding the mouseover text of that special effect to the card's display would go a long way to making things more transparent. Finally, I love the global enchantment idea. This is the root of an awesome game -- keep it up!
Good game, somewhat buggy: I've had the clock freeze on me before completing the objective, coins float in a cloud without being collected, and problems with having to click four or five times before patient zero finally gets infected.
lovely concept. Needs some flexibility in the difficulty curve -- right now, you either solve the puzzle, or you don't, and if you don't you're just stuck. Perhaps accumulating "weenie" points might grant an extra piece in some levels, or give a hint -- perhaps by placing one of the pieces in correct place for the solution and locking it there. I've been one piece shy of solving 15 several different ways now, and it's starting to grate.
Axoren is right -- the "stickiness" of machinery lag frustrates the pure planning. I know I'm not playing on a high-end machine -- that's part of the reason I like thinky, rather than twitchy games. But running the same simulation over and over and getting different results is...frustrating.
Being able to set an option for run speed would improve the game immensely -- and being able to adjust run speed/direction or step through while running a program would also be a fine conceptual aid.
Great game, though, even if a few components are frustrating.
RTS lives and dies on the quality of its controls. In the last few missions, the slowdown was so terrible, I often would get wierd artifacts and eventually gave up on anything more interesting than sending my drones to a corner of the map...which usually to at least two tries. The countdown timer was running at 1 second every 2-3 real seconds. It was terrible.
Also? The build queue is both opaque and SLOW. one trickles out units in a most frustrating manner, and screwing up the build queue (due to overestimating the enemy or misclicking) takes forever to clear...
More explicit unit descriptions would help.
The amount of lag, especially when attempting to build defenses while under attack, is...prohibitive. If you don't mean for people to build anything at night, you can do that, but some levels are wickedly difficult without nightbuilding.
 "bit Dungeon"){kind=icon}
 "Fracuum"){kind=icon}
 "Pick and Dig 3"){kind=icon}
 "The Codex of Alchemical Engineering - Magnum Opus Challenge"){kind=icon}
 "Cardian"){kind=icon}
 "ClueSweeper"){kind=icon}
 "Infectonator!"){kind=icon}
 "faze"){kind=icon}
 "The Codex of Alchemical Engineering"){kind=icon}
 "Drone Wars"){kind=icon}
 "Super Energy Apocalypse"){kind=icon}