Hello! I am a huge fan of Tower Defense games, especially of the endless variety such as Desktop Tower Defense and Onslaught2. As such, literally the ONLY level I play is Medium Level 10, Minefield. And I can proudly say that I have gone up in rank from #249 (Wave 187, 650 mil points) to Rank #67 (wave 199, 811 mil points) to RANK #19 (WAVE 205, over a BILLION POINTS! FRONT PAGE!). I am quite proud of reaching rank #19, and someday, I hope to reach #1, although that seems pretty unlikely.

That said, I can only guess how the people ranked above #10 got such high scores. I have my own strategies (that i'll list below), but i will admit that reaching wave 205 took a phenomenal amount of concentration, timing and effort. So strategy is part of it, but your own willpower is important too :P

So here are a few of my strategies that I utilize(hopefully you notice them with my pictures I include):

1. Take advantage of the early weak creeps for score multipliers.
I used to be scared of the O creeps (the ones that are impervious to missiles) and try to set up a laser with a long stretch before they came. Then I realized that I was destroying all the other creeps with no effort, and that maybe I could have the creeps come super close to the exit. Creeps killed one square away from the exit get a x5 multiplier, and can get x10, x20 and x50 the closer they get. The x50 is if the creep is literally right on the exit. In my experience, using either a single blaster and a shock or level 5 thumpers, I've gotten to a x600 multiplier by wave 8. I believe this is how people in ranks 1-10 have so many points, while only reaching waves under 200. I will provide more detail if anybody asks.

2. Create long runways with locked-lasers.
Usually I work backwards. I create a long runway near the exit, and then upgrade them to level 3 as soon as I can so I can lock them. Then I create my maze with green blasters and upgrade the exit lasers so they take care of any of the creeps that manage to survive the maze (especially the O creeps). I then add more lasers (starting from the end of the maze) and lock them. I try not to overdo locked lasers though, usually 1-2 per long-runway, so I'm not robbed of laser-power. The exception would be the end level lasers, where i usually have 3 of them facing up, and locked. 

3. Upgrade maybe 8-10 blasters into Sniper Towers fairly quickly
Sniper towers (level 7 blasters) are useful in that they are your main creep killers in the early levels, while you muster up the money for Shocks and Missiles. even having a bunch of boosted lasers isn't fool proof, which is why the sniper towers are useful to pick off that rogue creep. Remember that if you sell them to make room for other towers, make sure to offset the killing power of the Sniper tower with another tower. Ex... for me, I usually try to make sure I have one level 7 missile tower to replace the level 7 sniper tower i sold. 

4. Build your path close to the Vortex Towers (and obviously, USE THE VORTEX TOWERS.)
I try to have the creeps pass by the Vortex Towers as much as possible. For those of you who don't know, Vortex Towers are the rainbow-y towers that come pre-placed in Minefield. Before I knew what they did, I used to upgrade them to the max and then pop them with a lot of creeps on the field to maximize the damage. Then I discovered you can link towers to the Vortex Towers to charge them up and make a boosted shot. This is essential in my #2 (locked lasers) strategy. Without the boost, the end-level lasers will be too weak to take down the creeps at the end of the level. 

I have my creeps pass by the Vortex towers as much as possible. I put 4 thumper towers in between the Vortex towers, as the benefit of stunning creeps near the vortex towers is useful. I'm not sure how useful thumpers are in the later levels, but whatever. They look cool. 

when you have many towers linked to the Vortex towers, energy is always short on demand. There have been many times that one creep slips by because my end-level lasers didn't have enough boost to take it down. It's important to ration the amount of towers you link to the vortex, because otherwise the energy won't go to where it needs to be. Ex... One time, I linked EVERY level 7 missile tower to one Vortex Tower. And I ended up being sorely short of super-powered missiles, because it would take forever to charge all of them at once. And sometimes, when all of them were charged and they all fired, many of the super-powered missiles were wasted because all the creeps were dead. 

5. Create a secondary path for the creeps so that you can "Juggle"
This is probably a very necessary strategy to score high. If you don't know what "Juggling" is, play Medium Level 8 to understand it better. Basically, it is to make the creeps change direction because their original exit is blocked. 

For me, the secondary exit needs to be somewhere in between the first exit. The creeps need to be far enough from the 2nd exit that they don't easily escape, but they need to be close enough that choosing the 2nd exit makes them change direction (being the shorter path to the exit). I've created many different mazes, and my favorite by far is the one I reached Wave 205 with. The 2nd path forces the creeps to pass by the Vortex towers again (emphasizing startegy #3), so in essence I can juggle the creeps next to the Vortex Towers for additional energy harvesting. It is also JUST far enough so that rogue-fast creeps don't escape. Also, if the creeps find the 2nd exit more efficient, but are far enough it, you can sell and replace a tower quickly to stall the creeps indefinitely. This is also one of my essential strategies and is really effective, especially if the creeps are next to Vortex towers. BUT BEWARE: If there are too many creeps on the field, the game WILL CRASH if there are too many creeps. This has happened to me many times, and is a partial reason why I reached Wave 205: Because i didn't want to risk the game crashing, and essentially gave up so I can have my score recorded. 

Here are some other random strategies that don't really have a writeup:

- Vortex towers, as they are upgraded, not only hold more energy but can absorb energy from farther away. I think they can absorb energy from as far as 2 hexes away.
- Shock towers are ESSENTIAL, but don't use too many. Space them out. At some point, if you have too many shock towers, you won't be able to kill anything. 
- As I read from somewhere on the forums, a level 7 laser is always better than a level 7 sniper. They have the same range and the laser has the benefit of hitting anything in it's path. The snipers are just good for early-level killing.
- I like to create a "reserve" of boosted-Missiles. Somewhere in the map where creeps don't often reach (like a corner), so that I can have a couple missile towers with full boost, ready to fire at the rogue creep that passes by. (see the upper right corner of the map, next to the healing hex) With my current maze, there isn't much of a reserve, but with other maps I've had reserves of 8 missiles near my secondary exit that have saved me. 
- Try to block off healing hexes completely, so there is absolutely NO CHANCE that a creep can pass by it. Often times when juggling, a creep can cut corners and sometimes they would pass over the healing hex and become completely healed. 

Here is my finished map. I made no changes after. (pic taken at a rare time when the field was cleared):

http://twitpic.com/wo8rz  (in case it doesnt show up)

And here it is finished:

http://twitpic.com/wo8sg  (in case it doesn't show up)

I hope this was useful, and I'd appreciate your feedback! Again, I am not the best at the game. Rank #19, who gives a crap? But for those of you that are struggling with Minefield, this may give you some ideas. I figured this crap out by myself, and there doesn't seem to be a lot of people online who posted their mazes. Also, please comment if i missed any strategy.

To David: Awesome game. I'd love to see a blank field one day, and the ability to place down Vortex towers. Maybe you can limit the number of vortex towers to 4? Minefield is my favorite level, but as implied by the name, there aren't that many maze options. Blank field would be awesome!

-wes-

Edit: changed all "trillions" to "billion" as my wording was wrong.
Edit: Haha. I just finished a run and i got to wave 211, with a score of 1.27 BILLION! Rank 8! WOO!  

Edit 2:

1.51 Billion points! Rank 4! (For now...)

Edit 3: RANK 2! http://twitpic.com/141wi6

Edit 4: HATE RANK 1. HATE YOU.
 

Honestly, Rank 1 is such a cheater. How the hell did he get to 261?!