Time Invested: 1 Hour+
Information: This achievement is heavily based on luck, but requires some level of skill.
The goal is to COMPLETE the 10th level of I, Zombie Endless, thus obtaining a 'streak of 10'. To unlock the "I, Zombie" gametype, I believe you must first complete Adventure Mode and then finish the first 9 levels of I, Zombie.
The general idea is to eat each brain using as few sun points as possible. Reaching level 10 (and completing it) will require a well thought out plan on every level, and quite a bit of luck from the randomly generated levels.
The best approach is to restart the beginning over and over until you feel that the first level's plant placement will leave you entering level 2 with at least 750 sun. I've managed to finish level 1 with 1,150 sun left over, but even then I was only able to make it to level 9.
Since each level is randomly generated, and every level will be different, I'll lay down some cold hard tips.
1. Find a good first level (as mentioned above).
2. Take your time! Planning is very important.
3. Always consider using every zombie in each situation. Sometimes the Disco Zombie (even though he costs 350 sun) will be the most cost effective in any given situation.
4. Practice. Learn the amount of damage each zombie can sustain. This will help you save sun. Where a conehead zombie will reach the brain, why waste a buckethead?
1. Standard Random 1 - This level contains one magnet, one threepeater, one starfruit, one bungeeplant, and several peashooters (frost, repeaters, and split peashooters).
2. Standard Random 2 - This level replaces most of the peashooters with chompers, and adds a walnut, but keeps the rest the same mostly.
3. Scaredy Shroom - Lots of scaredy shrooms, puff shrooms and sunflowers. Take advantage of the fact that the shrooms hide even when a zombie is nearby in another lane. You should be able to complete this level using 5 conehead zombies (one for each lane). This is the best level to get, and unless you're a master strategist, you probably won't beat level 10 without encountering this level along the way.
4. Magnet Flower - Not sure if it's fume shrooms or chompers, eitherway this is another decently easy level. Mostly littered with magnets, there are some sunflowers and like I said either some shroom type or chomper. Another great level.
5. Instant Death - This level is one of the worst to encounter. There are many chompers, potato mines, and squashes. On average I lose about 500 sun completing this level. Two approaches I use are to either sacrefice lots of imps to the mines, chompers, etc, and clean up with coneheads, -OR-, if the situation permits, use a Disco Zombie. His summons can help clear two lanes which may be cheaper than wasting lots of imps.
There are other level types, but these are the main ones that I can remember. The Magnet Flower and Scaredy Shroom levels are quite rare. Playing through roughly 70 levels, I've encountered the Scaredy Shrooms three times and Magnet Flower once.
1. Imps can withstand 2 hits from Peas, Spikes, and Fumes. The third hit will behead them. Not sure about kernels, butter, or flaming peas. If a lane has only one spike, an Imp should do the job, unless the spike is in front of the brain.
2. Keep an eye on starfruit, they can ruin your sprinting imp.
3. If a lane looks tough, know that a miner zombie first to clear and then an imp to get the brain costs the same as a football zombie, but is garaunteed to work. (Example: The lane is, from left to right, Kernal Pult, Fume Shroom, Frostpea, Puff Shroom, Sunflower.) This assumes there are no threepeaters or magnets nearby, and no potato mines or split peas on the specific lane.
4. Potato Mines blowup miner zombies. I know this is easy to figure out but I didn't know this until it was too late. Keep it in mind!
5. Two coneheads are nearly as powerful as a football zombie, if they are launched at the same time. This is especially good vs. kernal pult because it only takes a few butters to ruin your football zombie if the lane is packed with shooters. Whereas, if there are two zombies, the likelyhood of them being buttered at the same time are low, even with two kernal pults.
Hopefully some (or all) of these tips will help you to beat level 10! Remember, it's highly luck based and if you run into a great level, don't get cocky. When I earned the achievement, on level 7 I had 2,500 Sun. By the end of level 10, I had 150 sun leftover (due to Instant Death level). Good luck!