This is my first try at writing a walkthrough. It is not complete, but perhaps it can be of help to someone. Perhaps modifications and alternate strategies can be pointed out to help me get through it.
If the formatting comes out messed up, I apologize as well. I typed it up in Notepad, but when pasting here, a lot of line breaks appeared. I tried removing them, but I'm not sure how successful I was. (Hint to Armor Games: Allow preview of posts!)
My thanks to Gantic who set me on the track here. Without his advice I couldn't survive past the first boss.
Medium Level
Start with one Basic Arrow Tower. Place it in the first u-bend, one square away from all sides. Upgrade it once.
Send the first wave of greys.
Upgrade again.
Send Wave 2 (Common Greys).
Upgrade again.
Send Wave 3 (Red Groupers). They will pick up the elements, but the tower will defeat them on the way back, leaving the elements at the far edge of its firing range.
Upgrade again.
Send Wave 4 (Yellow Runners). They will move the elements a little further into the firing range of the tower.
Send wave 5 (Red Groupers). Again the elements will be moved a little further along the path.
Send Wave 6 (Common Greys). This wave will be easily defeated.
Send Wave 7 (Boss). Once again, one of the elements will be moved, but the Boss will be defeated.
After this, click on Store and pay 1 credit to move all elements back to their starting position.
Send Wave 8 (Common Greys). No problems here. At the end of this wave, sell the arrow tower and purchase a Chain Gun. Place it in the same position the Basic Arrow Tower was in.
Send Wave 9 (Red Groupers). Again, they will move the elements to just inside the firing range of the tower.
Send Wave 10 (Yellow Runners). No problem here. Do not upgrade your tower, earn interest on the money in your account.
Send Wave 11 (Great Resistors). They won't make it far.
Send Wave 12 (Fixer-Uppers). They will all die unpleasantly.
Send Wave 13 (Shifters). They will again move the elements about half-way into the firing range of the tower. Go to the Store and pay 1 credit to replace the elements in their starting positions. Upgrade your tower one level (M2). Sometimes the Bosses can be defeated without the upgrade. That is best, but it is tedious to have to replay the entire game, so the upgrade seems advisable. Also, the each Boss is worth $240, so letting one boss escape is a bigger cost than paying for the upgrade.
Send wave 14 (Red Grouper Bosses). Afterward, go to the store and reposition all the elements.
Send wave 15 (Armor Plated). They will be defeated, but not before they haven't moved the elements back into the firing range of the tower. If you did not purchase the tower upgrade in the previous step, then do so now. If you purchased an upgrade before the Boss level, don't purchase one now. Your tower should be at M2 level here.
Send wave 16 (Red Groupers). They should die after carrying the elements within firing range again. I chose to reposition the elements.
Something you might want to consider is to sell your tower at this time and reposition it. Selling incurs no cost and with the wider range of the upgrade, the tower will be more effective if positioned one square further back from the "bottom" of the U-curve.
Upgrade your tower to M3 level.
Send Wave 17 (Yellow Runners). Repositioning the elements was wise, the groupers only were killed after the second full pass.
By now I've played so many times I was in no mood to experiment. WHY IS THERE NO SAVE OPTION IN THIS GAME??
Send Wave 18 (Great Resitors). With the tower at M3, they all died early.
Send Wave 19 (Fixer-uppers). They didn't stand a chance. Now reposition the elements to their starting position.
Send Wave 20 (Shifters). Afterward, reposition your elements to starting position.
Here I went to the store and purchased the Red element. Then I purchased a Splinter Tower and positioned it in the first sharp (right-angled) corner right near the entrance. I purchased one upgrade for the splinter Tower (M2) and also purchased an upgrade for the Chain Gun to M4. If you can, sometimes you might need the chain gun at M5 level, so consider doing that.
Send Wave 21 (Yellow Bosses). That M4 upgrade was necessary, At some instances, I needed to upgrade to M5!
Reposition the elements.
Send Wave 22 (Common Greys). As they predicted, they didn't stand a chance. They will die with the tower at upgrade M4 level, so if you didn't upgrade previously, no need to upgrade after the Boss wave.
Send Wave 23 (Red Groupers). They also died on the first pass.
Send Wave 24 (Yellow Runners). Fast, but not fast enough. They all turned into toast!
Send Wave 25 (Great Resistors). Toast anyone? In some levels, here I repositioned the elements back to starting position.
Send Wave 26 (Fixer-uppers). Toasted.
Send Wave 27 (Shifters). Even their invisibility couldn't help them. Go to the Store, purchase the Yellow element.
Purchase a Sniper Tower Mk2. Position it in the second U-bend in the path, about 4-5 squares back. As you upgrade it, it's range will increase to cover the lower part of the U-bend.
Upgrade it to M4 level.
Send Wave 28 (Boss). He should die somewhere on the return path, in range of the sniper tower, leaving one element there.
Send Wave 29 (Common Greys). Move all the elements back to starting positions. Weapons check. Tokens:21, Bank balance: $1825, Splinter Tower(M2), Chain Gun (M4), Sniper Tower Mk2 (M4).
Send Wave 30 (Red Groupers). They will barely manage to move the one element the Boss moved.
Send Wave 31 (Yellow Runners). Reposition all the elements after this wave. Go ahead, purchase the Blue element.
Sell the Sniper tower. Upgrade the splinter tower to M4 and the Chain Gun to M5.
Send Wave 32 (Great Resistors). Reposition the elements.
Send Wave 33 (Fixer-Uppers). In hindsight, it might have been better to purchase another Chain Gun and positioned it in the second U-Bend. I would have upgraded it somewhat. Reposition all the elements. Here I caved - I didn't want to experiment too much, because I didn't want to replay this many levels if I failed. So I purchased another Chain gun tower and positioned it in the second bend - in the center, but two squares back from the bottom. I had enough money to upgrade it to M3 and did so.
Send Wave 34 (Shifters). They all died without reaching the elements.
Send Level 35 (Self-healing Boss). Phew, he barely died. There was enough time that he was not under fire to almost completely regenerate. Perhaps upgrading the second Chain Gun would have been a better alternate strategy. Remember to reposition the element the Boss moved! (I forgot and had to repurchase it.)
(Another option I explored that also worked to the same degree of "almost escaped" was to purchase three chain guns and position one in each U bend and the 3rd near the elements. Afterward, sell the 3rd Chain gun so that you can ear interest on the money.)
Level check: 28 tokens, $2,207 in the bank. Splitter Tower (M4), Chain gun in first U-bend (M5) a nd Chain gun in 2nd U-bend (M4). Come on, you greys...
Send Wave 36 (Common Greys). No problems here.
Send Wave 37 (Red Groupers). I briefly considered upgrading either the Chain Gun or the Splitter but decided to chance not doing so. Return the elements to their starting positions.
Send Wave 38 (Yellow Runners). Close enough, they all died but fairly near the end. Reposition all the elements. Upgrade the second Chain Gun to M5.
Send Wave 39 (Great Resistors). Reposition the elements.
Upgrade the Splinter Tower to level M5. Buy a Basic Arrow Tower. Position it as close to the elements as possible and upgrade it as far as you can (M4 in my case). This is to keep some form of firepower on the next wave of self-healing creeps.
Send Wave 40 (Fixer-Uppers). The precautionary Arrow tower was not necessary, the fixer-uppers died in the cross-fire of the second Chain Gun.
Send Wave 41 (Shifters). Take your chances and don't reposition the elements before releasing the next Boss wave.
Send Wave 42 (Shifter Boss). This Boss got away with one element.
In another experiment, I was at this level with $3,267, so I installed two Mk2 Sniper towers - one in each U-bend. Each was fully upgraded, so also slowed the boss down when they hit him, which they could do even when he was invisible. The Boss still got away.
Send Wave 43 (Common Greys). Reposition the elements.
With $3,795 in the bank, I had to rethink how I would tackle the Groupers in the next level. I tried buying two more splitter towers, positioning each one in the curve of the U-bend.
Send Wave 44 (Red Groupers). That worked. All the Groupers died.
Send Wave 45 (Yellow Runners). They managed to escape with two elements. I repositioned the remaining two elements. Perhaps installing Glue Guns might have worked better. I might try that if I ever replay past this level.
I sold all the splitter towers and threw my resources into two more Chain Guns - one right near the entrance and a second one on the far side of the 2nd U-bend. With the remaining funds I bought two jet towers that I positioned inside each U-bend. The first one I fully upgraded to M5 level and the 2nd one I only had enough to get to M2 level.
Send Level 46 (Great Resistors). All died. Reposition the elements.
In order to maintain continuous damage on the next level, I sold all the additional equipment I acquired for the previous level, except for the 3rd Chain Gun I kept positioned near the outside of the 2nd U-bend. I installed two splitter towers immediately next to the concrete barriers at each end of the track, one at the entrance and one near the elements.
Wave 47 (Fixer-Uppers). Moderate success. Some creeps escaped, but my remaining three elements remained intact.
I decided for this round to simply see how I would fare if I upgraded the splitter towers to M5 level.
Send Wave 48 (Shifters). Moderate success. Some creeps escaped again, but my elements remaind in the playing field.
I sent my elements bac to their starting positions, and kept everything else as-is for the next level.
Send Wave 49 (Common Grey Boss). Finally I killed everything on a level again. Reposition the elements.
I decided to trade in the Spliiter towers (fire) for Glue Guns to slow the next level. To do this I had to repurchase my Blue element from the store (5 tokens). I purchased three Glue guns - One each in the curve of the U-bend, the 3rd diagonally one square away from the inside of the right-angle bend near the elements, where the 3rd Chain Cun could fire into it's zone.
Send Level 50 (Yellow Runners). The end. I lost all my elements. I didn't kill any of the Yellow Runners.
Easy is so easy, you can pile a bunch of turrets along the path without a strategy in mind and still win. Medium is hard enough as it is, but perfecting a strategy for medium could also mean perfecting a strategy for hard, although hard gives the guns less chance to fire, however, I think I've found a way around that.
I've made it further after I've discovered a problem with the DPS strategy.
Levels complete: 50 (could've been more but I forgot to reset) Creeps killed: 849 Gold Earned: 13718 Total Score: 45342 Tokens remaining: 2
Disregarding my lack of regard with token conservation, the score looks rather nice. The damage per second (DPS) strategy using G/R/Y works very well for the easy level, but for harder levels it just sputters until its doing not much. What's needed is an area effect (AE) strategy using P/B. Switching out from DPS to AE at the later levels means the AE towers don't have the extra strength it could have gained through exp.
Once the Chain Gun starts to max out, employ Glue Guns, not Splinter Towers, and a couple Jet Towers (You'll need to put them up early on since they'll have more exp which means more splash damage, but I'm not sure how early. They don't necessarily have to replace Chain Guns, but they damage more creeps per second if the creeps are piled on top of one another). Glue Guns are much cheaper, upgrade is constant, and constantly effective for all levels, maxed is ~170% slow. Since creeps recover speed over time, putting 4 Glue Guns in the same area may completely stop several creeps and slow the rest to a crawl as slow is an AE. Placing Glue Guns close together is most essential. (Jet Towers have massive range, so it doesn't matter much where they're placed so long as they have coverage of the maximum slow AOE.) I'm not entirely sure if it is possible to completely stop all creeps with 5+ Glue Guns, but it is certainly possible to slow them down enough to clear them out about as well as the DPS strategy can.
Made a mistake. What's needed is not just Glue Guns and Jet Towers, but simple Sticky Towers, lots of them. They're cheap (25 ea. 125 to max) and very effective.
Silly me I thought when I was going through a walkthru it was a strategy on how to beat the level....I already had figured out several ways to not beat it.
The First walkthrough vastly over complicates it. Starting with two green towers is frankly quite a bit less tedious. On easy and medium (not as much on hard) you can fairly easily beat all the way to mid 40s by spamming upgraded simple green towers. at 46 or 43 depending on the difficulty sell them and by the better fire tower and upgrade it three times then 4 or 5 chain guns and upgrade them a couple times each. if you place them well and sell the farthest ones as they become useless you should be able to stop at least one of the final bosses and win. Usually my score is about 48-51k but I haven't written it down.
