Rounds 1 - 4
Round 1: Set your Gun Tower above the ‘19’ block and there’ll be enough runners to allow you to upgrade it to level three.
Round 2: Let your level three gun do the hard work on this round for you.
Round 3: Set down a new Gun Tower in the middle of the map (beside the ‘8’ block), upgrade it once and then when the units are down, upgrade it to level three.
Round 4: Once you’ve earned $5, place a new Gun Tower directly above the first one you put down, this will help clear the map for you.
Rounds 5 - 8
Round 5: Before round five starts, drop a Gun Tower near their entrance (in between the ‘1’ and ‘7’ blocks) and then another one directly below the middle Gun Tower. Upgrade this tower to level two. Three Fokkers will show up, your existing formation will see to all three of them.
Round 6: At the top of the map another block will vanish, place a Gun Tower in its previous location. Once you’ve earned $5, place another one directly below it and then when the next $5 balance rolls around, place one two squares to the left of this tower.
Round 7: Nothing to do this round, just sit back and enjoy the cash increase.
Round 8: Upgrade the central tower to level three and then when the block near the top-left corner vanishes, place a Gun Tower in its place. When you reach $5, place a new Gun Tower to the right of the very middle tower and then another one two squares right (creating a U-shaped bend).
Rounds 9 - 12
Round 9: Set a Gun Tower directly opposite the entrance and when you have $16, upgrade the two towers in the bottom part of the U-bend to level three.
Round 10: Three Fokkers will now appear at speed across the middle of the map. You’ll dispatch the first two fine, but the third will escape. Use an item by the exit now if you want that clean sheet score line.
Round 11: There’s a lot of runners in round 11, so before it starts properly, lay a third Gun Tower near the entrance (pushing them up), then start dropping Gun Towers downward on the second column (as your money increases throughout the round).
Round 12: Now it’s about upgrading your existing Gun Tower maze with as many level three towers as possible this round. Towers in the middle of the screen and/or on the inside of U-bends are the ideal ones. Oh, and if you have any items; now’s a great time to drop one by their entrance.
Rounds 13 - 16
Round 13: Upgrade a couple more towers and if you want to let no-one through, then you’ll need an item by the exit to dispatch the last Fieldrunner in the pack.
Round 14: Replace the newly disappeared block (by the entrance) with a Gun Tower, upgrade it to level three, then do the same three squares to the right.
Round 15: There’s plenty of runners in this round, so item-bearers can speed things up by dropping an item by the entrance. Now upgrade a couple of towers (but save $20 for the next round).
Round 16: Three more cubes will remove themselves from the map, so extend your maze by placing four turrets across the south side of the map (see the screenshot above). Spend your remaining money on tower upgrades.
Rounds 17 - 20
Round 17: A line of Dirty Hogs will show up, but don’t worry, your towers can handle all of these.
Round 18: This time, a bunch of super speedy scramblers will dash across the map. if you’ve got any items, now’s a great time to use one.
Round 19: Upgrade a couple of guns and then save your cash as the Sidehackers enter the map, you’ll be wanting to buy a Flamethrower Tower and a couple of Gun Towers in the next round.
Round 20: Plug up the gaps that have just appeared, then drop a Flamethrower Tower on the south part of the map (it’s more effective at the end of the column).
Rounds 21 - 24
Round 21: Now’s a perfect time to drop an item as there’s a massive bunch of Super Troopers about to run around your maze. Upgrade your Flamethrower Tower to level two once you have the $40 needed.
Round 22: Focus on upgrading the Flamethrower Tower to level three ASAP (so keep an eye on your cash levels) as this’ll help make short work of the Scramblers. It’s also worth fully upgrading a few more Gatling Gun Towers whilst you’re at it.
Round 23: Plug the new holes in your maze first, then wait for the Super Troopers to show up. There’s enough of them to allow you to buy another Flamethrower Tower next round.
Round 24: So swap out a Gun Tower two squares up from your current Flamethrower Tower and drop another one in its place.
Round 25: Upgrade the new Flamethrower Tower ASAP and then once the fifth Fokker enters the screen, hit that switch and clear the level with a nicely timed Airstrike. Nice work!