I made this run with all permanent upgrades, so not really for new players.

Update: I found that this strategy still work for relatively bad RNG (eg. relatively early split and little to no loop around path)



Update 2: I used the same strategy and found it to also work in 2x defense. I screwed up and chose mana bolt at level 36 and it almost costed me a very good run.

If you don't have the time to read through the full strategy, here is the summary:

1) Select Banditry and University as early as possible (more in Upgrades Strategy section).

2) Pick as many Critical Chance cards as possible.

3) Try to lead path to loop around as much as possible. When you see a path turn or split, extend the direction that has the potential to loop around first.

4) Pay attention to Mobs and Boss to deal with at different stage of the game when choosing upgrade cards and target priorities (more in the Upgrades Strategy section and Mobs and Boss section).

5) No mana bolt.

6) No leveling up of any single tower. Just spam towers on all elevated tiles before you get your first university (more in Mobs and Boss Strategy section).

7) DPS is relying on D.O.T.S, cards upgrades, Universities, x2 Critical and sheer number of towers to chip away Shield, Armor, and Health of mobs. As shown in the attached screenshot, I spread Ballista tower all over the map.



8) Make sure to have some of the Ballista Towers target priorities set to Progress. This is actually better than setting Near Death to target Vampires or Fastest to target bats.

9) Invest in single damage research in University to save golds and I only invested to raise the chance to 15%.

Cards that i will always pick when I see them in the order of priority:
1) Banditry
2) Research Breakthrough +critical damage %
3) University
4) Longbow, always pick Longbow over damages upgrades and Damage Over Time (D.O.T) cards upgrades.
5) Scholarship I, only after I have picked University. No Scholarship II or higher unless I have no other choices.

I view the game to have 4 main stages and 3 minor stages.

The 4 main stages are:
1) Before Level 15 Boss (Oogie)
2) Before Level 25 Boss (Zombie Oogie)
3) Before Level 35 Boss (Robo Oogie)
4) Final Boss Stage (Big Brain Oogie)

The 3 minor stages are at:
1) Level 20 to 22
2) Level 30 to 32
3) Level 40 to 42

The 4 main stages are very important in guiding me to select what upgrade card to select. While the 3 minor stages are important for me in Tower Placement strategy and Tower target Priorities selection (More in Mobs and Boss section).

1) Before Level 15
Here, my first priority is Health damages and Bleed. I will choose Broadhead Bolts I (+1 health damages) or Jagged Heads I (25% Bleed) over armor or shield damages. I will only choose armor or shield damages after I got Broadhead Bolts I or I have no other choices. The selection principle is to try to make sure that Health damages is higher than both Shield and Armor damages at this stage. Same goes to Bleed, I will make sure I have higher Bleed over Poison and Fire D.O.Ts. Unless RNG given me really bad cards options, then I will make sure I have higher Armor damages over Shield Damages but it is the other way round for D.O.Ts, I will try to get higher Poison D.O.Ts over Fire D.O.Ts at this stage.

I will choose Bleed Them Dry over Armor or Shield damage upgrade cards AFTER I got Jagged Heads I (25% Bleed). If I don't have any Bleed D.O.Ts, then I will choose either Armor damage or Poison D.O.Ts upgrade over Bleed Them Dry. Bleed Them Dry is good to have but not absolutely necessary at this stage.

I will ignore both Kill Them with Fire and Slow and Steady at this stage.

Frost Bolt and Creeping Cough (to slow the mobs) are good to have. But not my highest priority now. Since I am only focusing on upgrading Ballista tower, I will more often than not getting them in mid and late game stage. If the choice is between slowing mobs down and armor or shield damage, I would pick armor or shield damage at this stage.

2) Before Level 25
Now, I switch my priority to Shield damages and Poison D.O.T. Again, I will only select Heavy Shafts (+1 Armor damages) or Flaming Bolts (25% Fire D.O.T) after i have Enchanted Bolts I (+1 Shield damage) or Poison Bolts I (25% Poison D.O.T) or I have no other options. Now, my selection principle is to make sure that Shield damages is higher than Armor damages.

Here is the time to choose Slow and Steady over Health damages and Armor damages card. So I will make sure I pick it, AFTER I got at least 25% Poison D.O.T. Usually, at this stage of the game, I would already have gotten Poison Bolts I (25% Poison D.O.T).

Mob slowing cards (Frost Bolt and Creeping Cough) are still good to have but not necessary yet.

3) Before Level 35
Now my focus is Armor damages and Fire D.O.T. So I will always choose Heavy Shafts or Flaming Bolts over other damages.

Kill Them with Fire is important. I can still survive without it but it is harder to survive this stage without Kill Them with Fire as it also unlock both Slow Cooker and Fire and Frames which are important at this stage.

Frost Bolt and Creeping Cough is important now. I will try to get at least one at this stage.

4) Final Boss Stage
Here, I will try to max out all Bolts cards except Mana Bolts. I don't use Mana Bolts as it takes away at least 2 other damages upgrades card opportunity as I will have to select at least 1 (Mana Bolts and Mana Bank) over other damages or D.O.Ts upgrades. Mana Bolts also takes away gold for Ballista towers, Universities and reseach for Mana Bank placement. I would rather place more Ballista Towers over Mana Banks. Without Mana Bolt, I find that level 1 Ballista Tower has over 360 damages to Shield, 50% x2 Critical at level 44, just for Maxing out all other Bolts cards, Critical hit cards and other damages upgrades and D.O.Ts cards. I don't need Mana Bolt.

I will try to get at least all 3 Bleed Them Dry I, Kill Them with Fire I, and Slow and Steady I. Make Them Suffer is good to have but not necessary.

Frost Bolt and Creeping Cough is important and will make the run much more survivable at this stage (especailly Level 42).

In single tower run, I found that I am more likely to be over run by mobs rather than Boss. For Oogies, so long as I pay attention to which damage and D.O.Ts to focus on, I am generally doing fine. But for mobs at the 3 minor stages mentioned in the previous section, they are actually a lot harder to deal with using Ballista tower alone.

So the strategy is to try to lead the path to loop around as much as possible so that the Ballista Towers could shoot at them 2 or 3 times in their journey to rush my base tower and place as many Ballista Towers as the amount of golds I can buy.

With single Tower Ballista run, I find that upgrading a few strategic towers is not as good as putting down more towers to address any sign of mobs leaking through the defense. However, this is only true for level 40 or above after I have got the mobs slowing cards (Frost Bolts and Creeping Cough), Longbow, and almost all D.O.Ts cards. The Level 1 Ballista Towers at this stage will have the slow effect and high enough x2 critical % (high 40s) to slow down the mobs and chip away their size. What I find is with this strategy, it is better to have a few more bolts than one substantially bigger bolt.

1) Before Level 15
For Ballista Towers near the Base Tower set target priorities to progress only.
Put some Ballista Towers at +3 elevation as much as possible along the path and make sure that the mobs are always within the firing range of the Tower. Some of the Towers should have their top target priority set to Most Health, some set to Most Armor but leave some in Progress. I don't set the second or third priorities and always leave them in Progress.

Put Ballista towers around all the houses. This always pay off in the long run.

I don't normally spend all the gold to put down Ballista towers at this stage, but I will try to put Ballista on all elevation +3 and +2 along the path and corner, the key is to make sure that the mobs are under constant Bolts bombardment along the way. I don't upgrade any tower, I just add towers when I notice any sign of Mobs overrunning me. If I run out of +3 or +2 elevation to place my tower, i will start choosing strategic +1 elevation tiles to put my towers to address any leaks. Then I will try to lead the path to loop around as much as possible.

When I come across a split, i will extend the direction that has the potential to loop around my base tower first. I find this strategy can sometimes able to lead the path to go near my base tower or even loop around my base tower and let the Ballista Towers in my base tower to chip away the size of the mob and level up at the same time.

2) Level 20 ~ 22
Here, I would pay close attention to any sign of Mobs leaking through my defense. This is where I would put down Ballista that could shoot at 2 or 3 paths, or the potential to shoot at 2 or 3 paths with the Longbow cards upgrades. Here I would normally set my towers target top priorities to Most Shield, Least Health, and Progress.

Mobs to watch out for here are Vampires and bats.

3) Before level 25
To prepare for Zombie Oogies, I will try to make sure that I got at least 25% Poison D.O.Ts with Poison Bolts I before level 25. This is feasible because I only choose 1 tower upgrade cards.

4) Level 30 ~ 32
Armor regeneration is a huge problem, both Kill Bots and Tank Bots are to watch out for. They could regenerate their armor rather rapidly and will shoot fast traveling missiles once their armor are depleted. So watch out for them after killing Zombie Oogie.

They would normally start appearing at around level 30, so I always make sure to place more towers with top target priorities set to Most Armor, Least Health, Fastest, and Progress. It's important to leave some Towers top target priorities to Progress, else I would notice mobs at the front of the pack being ignored by most of the towers as they are busy engaging Most Health, Most Shield, Most Armor etc.

At around this time, I would find myself placing Ballista towers in the middle of the run to address sign of mobs leaking, for these towers, i will just leave their target priorities at Progress.

I normally don't need to spend all my gold yet to place down Ballista Towers but I will keep putting down Towers when I see that the Mobs are edging closer to my base tower. I normally try to be strategic when putting down towers at this time, focusing on their ability to shoot at 2 or 3 paths. Less on their target priorities. Leaving the target priorites at Progress works, because at this time, I would have a lot of Ballista Towers spreading all over the map.

University and Research
Hopefully by this time I have found some shrines to place down University. I would usually upgrade the research on Armor in 1 university and the rest on Shield. In my opinion, anything more than 15% is not a good investment of gold, as I would rather spent the gold on placing more towers. For every University, I would only focus on spending gold on researching on only 1 damages, either Armor or Shield. I don't spend the gold to try to research 2 or more damages in the same university. I think it's cheaper this way to raise the + damage chances.

5) Before Level 35
With Fire and Flames or Slow Cooker, Robo Oogie is not difficult to deal with. Also Frost Bolts and Creeping Cough are important in helping me to get to level 35.

6) Level40 ~ 42
Here, I would watch out for Vampires, Cranial Carnivals, and Hovering Portals. They are tough with very high shield regeneration and some of them like Vampire could transform into bats when their shield is depleted and Cranial Carnivals will shoot out fast running mobs. Longbow, Creeping Cough, and Frost Bolts are essential to survive this stage.

Here, at the end of every level I would spent all the gold I have on placing down more Ballista Towers on elevated tiles.

7) Final Boss stage
Big Brain Oogie will usually be no match with the sheer number of towers in the map. Since I don't need to invest my gold in any thing other than Ballista Tower, Universities and Research, I spent all my golds in placing more towers up until level 45. I usually don't need to put down any more towers at level 45 and could just enjoy watching Big Brain Oogie being slowly burn away. Here, I need to stress the importance of leaving most of the Towers target priorities to stay as Progress, as the tower will all target the same mobs, will be able to kill most small mobs with one single round of volley of bolts.

The advantage of keep on placing towers will also be apparent when the slow effect of the tower would slow 99% of the mobs down and extended their time of being shot at by the higher level Ballista Towers. So even level 1 Ballista Towers are very good at level 45. They may not be able to do a lot of damage to some of the higher level mobs, they are still good enough to kill those fast running mobs with their high critical chance. My Level 1 Ballista Tower at level 45 has over 360 Shield Damages and has 40~50% of x2 Critical and they level up fast when dealing with the mobs in level 40 and above. The reason that they have high crit is because I will always pick crit chance upgrade cards when I see them over other damages or D.O.Ts card. Perhaps limiting cards upgrades to a single tower also helps in raising the chance of crit chance card appearing.