There are very few games I can think of that really feel as total and feature-complete as Gemcraft does. In terms of game design and "taking a concept to its logical conclusion" Gemcraft is one of those games that just does it right.
If you've never heard of it; Gemcraft is a tower defense game that started as a series of flash games before the developer, Game in a Bottle, eventually made standalone versions of the game. The one I'll be referencing for the rest of this blogpost is Chasing Shadows, because that's the one I'm still playing the better part of a decade later. Yes I know Frostborn Wraith already came out two years ago and is better in basically every way to this game, but I'm not going to talk about it because the art is ugly imo and these games are all infinitely long basically so whatever.
Gemcraft has a lot of neat design choices. Your mana is used to create your gems, which is also your health. I actually really like this because it means that an enemy slipping through to your orb only deducts a small amount of your resources instead of making you lose a limited number of lives- which would always invariably make me reset while playing any other defense game since you usually can't regain lives easily in those games. The game would be unrecognizable without this feature. The cost and reward of everything from gems to buildings to how much mana you get from killing enemies to how much mana is costs to banish them is all mathematically figured and quadratic. This means the game can be played basically infinitely with Endurance mode as things just keep scaling forever. But even the mana pool has a gimmick. There is a "maximum" amount of mana you can have in your pool, but when you exceed it, the pool doubles its current maximum while granting other bonuses. This means there are times where you have to be conservative and save up your mana for either defense against powerful monsters or to reach the cap, you aren't just spending every single point of gold you get as soon as you can. The game also does the thing I love and should be legally mandatory for any tower defense or citybuilder type game and let you take your level-winning setup and strategy and transition that, after beating the level, into infinite endurance mode. (The fact this was apparently removed in Frostborn Wraith is criminal). But the main draw of the game is the gems.
In most tower defense games, your primary tool and "point" of the game is the towers. Towers typically have unique abilities or types of damage they deal and are built in one static location, making positioning important. Towers can usually be upgraded multiple times or level up with xp from kills so you can keep up with the ever growing threat of the waves. Gemcraft flips this basic concept by making your primary tool your gems. Gems can be socketed into towers to fire, but can be swapped around as needed after a short firing delay. The different types of towers in most tower defense games (splash damage, slowing, etc.) are instead based on the gem's colors. This is built into the mechanics of the game; pure gems of one color have much stronger "specials" which are these properties, but gems with a mix of two colors or more have higher damage and stats. This is only a flat bonus for multicolor gems and based on the total mana investment of the gem (how many gems are mixed in) so the ideal gem setup is 2 or 3 colors in a single gem in a tower. Even the entire concept of the game is perfectly suited to its aesthetic theme- gems in real life have various cuts and colors, so it perfectly fits with a tower defense game with gems of increasing grade and mixes of magical and elemental properties.
The reason why this is so engaging is because pretty much the whole game is based around it and it built to support it as a system. So above I mentioned single color gems have stronger specials, right? So there are buildings in the game which are traps- which are built directly on the walking path. Traps attack really fast but do essentially no damage and have basically no range (since they are traps), but have a huge boost to specials. So usually you put gems of 1 or 2 colors max into a trap to apply their specials, where as gems in towers are gems designed to actually kill the mobs. But not only can you do that, you can actually use gems as bombs too, applying some of their effects and dealing a large amount of damage by sacrificing a gem. You use bombs to demolish buildings you've built or destroy random objects on the map, as well as monster beacons that empower nearby monsters. You can bomb your orb at the end of the path to permanently make banishments less expensive. You can even gem bomb incoming enemy waves to enrage them, which makes the monsters stronger and makes the wave have more total monsters- meaning you get more mana back then you invest but giving risk of making the enemies too strong.
On top of this, defeating enemies grants xp for campaign progression and you can replay a level to try and get a higher score. Automatically this concept just lends itself to tickle my brain. It's very Disgaea-esque, a sort of infinite recursive feedback loop where you bomb waves to make the game harder, beat it and get a higher score, and can immediately replay a level while stronger to get an even higher score again. It's the sort of addictive quality has made me continue off and on playing this same game and game series for years. I've never been any good at it and have never even gotten close to beating any of these games considering the fact they are all absolutely massive. I remember playing the first flash Gemcraft game and being floored by just scrolling the world map and seeing how far it goes, basically an odyssey, and watching the series grow and reiterate on itself over all these years is the exact kind of thing I live for. It's one of those passion projects where it just slowly perfects itself over time. I cannot recommend it enough if you're into that kind of thing.
However, Gemcraft CS has a few things about it I don't like, and mostly, it's based on the gems. The gem colors are a big part of Gemcraft but also change pretty much every game, and possibly because the developer feels the same way. Gemcraft CS has nine gem colors, but because of how they are set up, many of them don't feel useful or are too typecast in one role. See, when I play a game like this in how well designed it is, I kind of expect and wish the entire game is as tightly balanced and creative as it appears, and inevitably get disappointed when that isn't the case. It's not really fair to expect a game that is already really good to live up to some fantasy version of it I've invented in my head, but that's just how I feel.
Side note: Not specific to Chapter CS at all, but gem bombs have always felt wack to me. In the first few waves a single grade 1 gem can kill all the enemies it hits easily. Later on, gems fall off in power so badly they stop feeling like they do anything at all and are merely a waste of mana. Partially this comes from the tower-defense and economy mindset you adopt when playing a game like this. Gem bombs are destroyed when launched, so naturally they are not as efficient as putting a gem in a tower or trap that actually kills and stays around a long time. Naturally this means I never invest skill points into bomb or demolition related skills, making them even weaker. I don't know how viable a "gem bomb" and/or shrine based build would actually be but judging from my own experience and every community post I see about this game I can only assume its remains as a gimmick, not a core gameplay pillar. In a perfect world, gem bombs should be about as equally strong or viable as gems in towers or traps, so that ultra kill-gem you have in a tower should be able to clear like half the screen of mobs but you sacrifice all that mana you invested to do so to balance it. Trying to make this "balanced" with everything else seems basically impossible so I don't envy the game's creator at all in this task.
The same above also applies to shrines. Shrines have gone through a zillion different iterations in this series but the basic gist is shrines sacrifice a gem to deal serious damage, slow, etc. a group of enemies around the shrine. Much like anything else (and gem bombs), the gem's special also shows up in the shrines. However, Gemcraft CS has randomly spawning shrines, not buildings you can elect to build, so they don't feel like a part of your core strategy. Shrines also only hit a small area around them and have a set "special" effect, which have the same colors and symbols of your 9 gem types. For example, a "Slowing" shrine is blue and slows enemies like a blue gem, but it has nothing to do with blue gems and you can use any gem color in it; making it like a static thing that just appears on the map. Bafflingly, any gem you put in the shrine will have that same effect, just scaled base on the mana cost, and earlier versions of Gemcraft already had shrines that have different effects based on what gem you put within. This is how I feel it should already be; a shrine being a way to sacrifice a gem to produce a powerful effect in a small area and deal damage to enemies, with the shrine's damage and special effects being based on whatever gem is put inside of it. Also, Amplifier towers boost the damage and specials of towers and traps, but not shrines. Even more annoying; you can actually put an amplifer next to your orb in the map and that will strengthen it, reducing the amount of mana a banishment takes, but making shrines stronger or charge faster? Too far.
In Chapter CS you can't build shrines yourself, so that makes sense, but the lack of player shrines you can elect to build and boost feels like a missed opportunity. In the same way towers mostly deal damage and traps mostly inflict specials, dropping a gem bomb should be a way to expend a game to mostly deal damage, and a shrine could be a way to mostly inflict specials while also expending a gem(?). As it stands, the only shrine I care about at all is the XP shrine, which grants you a small amount of XP for hitting monsters by using a gem in it, and the HP shredding shrine (yellow) simply because I like to put a grade 1 gem in it at super late endurance levels to see how many tens of millions of damage it can do despite being worth 19 mana lmao.
But the biggest issue of the game by far is the colors.
In Chasing Shadows there are nine gem colors, but some feel redundant and not as useful. One color is Cyan, which used to be the "shock" gem, giving a chance to hold a monster in place while being shocked- a really useful gem in the older games. Now its primary purpose is "Reducing enemy health regeneration". This just doesn't feel very useful or strong at all, especially when green is poison gem, dealing damage over time. Why would I ever use one over the other? Another is purple, which is armor tearing. Purple on its own makes sense; monsters get armor that gets thicker and thicker the higher the waves go, and armor flatly reduces damage taken, so you need something to remove armor. But as classic video game logic goes, dealing more damage is usually better then debuffs. Both these gems also have the secondary problem of having situationally useful specials which you might want to use; but if you did care about their specials at all there would be literally no reason not to put them into a trap to maximize them. Meanwhile yellow (critical strike) and red (new chain-hit) are both extremely useful to put in towers. Now gems don't necessarily have to be perfectly and evenly balanced between if they should go in a trap or in a tower, but you can imagine in a perfect world they'd be equally viable in both, based on the player's strategy and tactics.
The other issue are the two scaling gems. These are bloodhound (black) and poolhound (white). Having bloodhound mixture in a gem gives it a small boost in power for its damage and specials based on the amount of hits it has made, and poolhound boosts the damage and specials of gems it is apart of based on your maximum mana pool. These gems aren't as common as the others but the basic idea behind these is a way to keep scaling your gems when you reach the point in the game where you can't actually scale your gems up any more, as well as a way to endure during really late waves in endurance mode. I don't have any issue with these other then that there is no strategy at all with them. If you have bloodhound you always want it either in a trap to farm hits or in your main kill tower that is constantly firing, and poolhound is only useful for gems in amplifiers or to be used as things like gem bombs or for shrines late game, since they get free stats as your mana pool increases. This is also already somewhat addressed in Frostborn Wraith, which has the "bloodhound" effect on making gems stronger with more hits as a default feature and mechanic of the whole game. I actually dislike this change somewhat because your most valuable gem is already going to be whatever you have the most investment in anyway; adding an XP element to the gems just further decentivizes certain strategies and encourage min-max trap farming nonsense which I don't enjoy as much.
So for these extremely minor complaints, I have drafted up these following changes.
Firstly; Armor. Armor is a cool mechanic in gemcraft and makes sense; it makes spamming many weak gems not an ideal strategy since enemies will block most of the damage and you need to invest more heavily in a few powerful gems. But gems do start to cap off in range and attack speed at a certain point, so you still need more then one gem to deal with swarm waves- too many small and fast enemies that can push past your slow firing killgem. It makes sense to have it. But Armor Piercing gems are very simplistic. Out of all of the "iffy" gems in this game, these are still the ones I care about and use the most, they are also one of the most common gem colors that are in maps along with orange (mana leeching) and green (poison), at least until you unlock the ability to forge a gem of any color in any map.
The issue with Armor-Shredding gems is that their usefulness as a secondary gem color in a kill gem is questionable at best. In order to fix this issue, I would say make the purple gems have the secondary effect of armor piercing as well. This means any hit with the gem not only reduces armor by a small amount, but gives the shot a small amount of armor penetration as well. So a tower with a purple gem also gets a damage bonus in the event the monster still has armor since it just ignores some. It should go without saying that any of these changes would naturally fuck up the extremely careful balance and math-work of the game creator- obviously this is just a conceptual sort of ideaguy posting, not a thesis in game design.
The second is the Suppression (Cyan) gem. As stated above, this gem just does not seem useful at all. The ability to reduce healing isn't that common in game strategies. By extension, if enemies did regenerate health super fast and this gem was made useful to mandatory, then the game would be almost excruciating to play on any level without them or just flat out annoying even when you do, because enemies, especially giants, would just be a huge pain in the ass to actually defeat. As it stands, I think these gems are sort of meant for 'anti giant' gems, since giants have a lot of health and armor and are the only enemies that will reasonably take more then one or two shots to destroy. Now I should mention that in super late game scenarios you actually need cyan because enemies regenerate so much health but similar to armor it feels like a losing strategy over boosting your damage and just overcoming them that way before you run out of juice. The other annoying thing about this type of gem is it only stops the regeneration that monsters have by default as opposed to reducing all healing effects on that monster, so even if you hit them with cyan they can still be healed by the random battle traits, like healing novas that monsters do when they die to heal other monsters next to them. In this case, I think having the Cyan gem work as a "stop all healing" works better. But what about in a tower? In a tower, the Cyan gem is a dead color to add to another gem, making it another trap-only sort of gem. My method to fix this, on paper, is to give it some kind of percentage health reduction or "echo" hit, where whatever damage the gem does is then echoed by every hit the monster takes for a short time afterwards. However even I have to admit this would probably fuck the game up beyond repair, because anything that deals percentage damage to monsters would quickly becoming the most OP gem in existence in a game with this much power scaling. Echo damage makes the most sense in that regard and is sort of already been added in FBW but is for that game's red gems. The idea of these changes is to make Cyan the defacto anti-giant and anti-unkillable boss gem type.
While typing this; even simpler idea. Make damage from Cyan gems reduce an enemy's maximum health + make health regeneration a percentage thing. This does both and already makes Cyan towers useful (more damage directly), but Cyan traps would be less useful unless it was reversed in some way. Still I think its interesting. The 'Echo' damage concept could work on its own here and just remove healing and regen except by special monsters all together (which is what FBW did anyway) to get the same basic effect. Also also giving gems more then one effect goes against some of the design principles of this game where every gem has one very simple line explaining their power, but there's a lot of complexity hidden behind it. Maybe reduce the monster's maximum hit points based on a percentage function with the traps doing a way higher percentage but the tower making better use of it, since it can actually deal damage.
Third and final is the Black and White gems. First off, I would absolutely change red back into being bloodhound. Looks better thematically and actually fits the name. Second; bloodhound and poolhound aren't bad gem types at all, just very simple and math-heavy. Using both on one gem doesn't really work so you're going to be using black gems on everything that hits a lot, and white on gems in amplifiers or passively. It's also a little complex and difficult to know if adding a white/black gem to a random gem is worth it or not. I can kind of see the point here; these are like base "damage up" gem types, where as the other types of gems have slightly more situational and supportive. For example; you could make a blue/green gem for poison and slowing for a tower, but should you add a white gem? Doing so gives it free damage and stats, but reduces the amount of its specials to poison and slow. BUT poolhound/bloodhound also INCREASE specials of gems it is a component part of as they scale. So is adding a white gem component like free stats or is it worse? If I want to make a mana farming trap, should I add black? Pure orange creates WAY more mana per hit, but black makes it stronger the more hits it makes. I get the idea of black gems kind of being like an "investment", something you make early to farm hits on for late game, where as other gems you can make fresh and use as you need- a reason I disliked the FBW change of making all gems stronger with experience. It's just less intuitive then it should be.
My other issue with gems of these colors, especially white gems, is because of half the appeal of this game. With a game with this many recursive and infinite growth systems; I really really like the idea of taking a powerful high-grade gem and just adding extra small gems into it. Maybe you find them by breaking open containers of the map, or you need just a little bit more damage or armor-piercing, so you just form a random grade 4 gem to mix with your grade 12 omega kill gem to boost its stats a little. You spend mana and time (gem takes time to resocket) in order to get a small power boost. My issue here is I don't actually think the game works this way and poolhound does the exact same thing with less drawback (don't have to spend any mana), which is one of the reasons why I dislike it. I feel like a core idea of the game is how modular and customizable your gems are, how they all combine into each other to become more powerful and beautiful, like a crazed gemcutter-wizard-alchemist-artist sort of roleplaying experience. Poolhound just undercuts this idea of slowly refining and improving your gems through incremental improvement because it is already the "passive scaling" gem.
How would I amend this? I would remove the Poolhound thing entirely. But I like the idea of having 9 gems and I think the white gems look kind of cool, especially when mixed with other colors. So instead I would have the white gems be "Charging" gem types. Basically they're an econ gem, like the orange gem, but instead of mana it generates charge for things. Every hit very slightly gives you energy for your battlefield spells; freeze, curse, tower enhancement spells, etc. Obviously this has a huge capacity to be broken, so the charge power would have to be limited some way; maybe it can only "overcharge" a spell once its already ready, giving a strategic layer of waiting to cast your spells when they're ready to go to build up a buffer so they recharge faster next use, or maybe they just have a hard limit of how much charge they can generate, like 15% total spell charging points per minute of game time, meaning it can help you get your spells out a little faster but you can't just farm infinite spells with the white gems. This would also be extra cool for FBW, because in that game there are new buildings and mechanics like Pylons. In that game, towers shoot at pylons when no enemies are nearby and the pylon will eventually gain a charged shot that deals a ton of damage- basically being a type of building that "stores" damage. White gems could be extra good at charging these. The other idea? Make white gems the banishment gem. Each hit reduces the amount of mana it takes to banish a monster up to a certain amount, essentially being a way to save mana as opposed to gain more. Once again, this would make trap versions of the gem much more useful and giving limited usability for towers- here I think an Echo damage mechanic would be the best. White gems reduce banishment cost AND deal damage when the monster is banished equal to the strongest hit a white gem did before they were banished. Then white towers and white traps basically act as a kind of endgame protection and "life generator" type of build and useful for super long endurance runs which is kind of their intended use already.
Anyways, despite all this whining, Gemcraft is already a great series of games and if you like tower defense games with lots of content, then you should check them out.