I saw the update and decided to give level 18 another try. It worked perfectly the first time. Big improvement! I'm changing my rating back to 4 stars.
Izzetmaster, just because it didn't happen to you doesn't mean it is not true. Lots and lots of people have reported problems with level 18 and synchronization bugs.
Bonus level three has some issues. When my third iteration is standing on the lever, the first crate makes it rise but the second doesn't. It will once I start jumping, but not having any movement just from the crate made me think it wouldn't work at all.
Level 18 is driving me nuts. My past selves won't stay synchronized, they do things slightly more differently on every repetition. This game should not have gotten badges yet with such an annoying bug in the basic gameplay.
I'm docking a point until the synchonisation errors are fixed. If the past versions of you don't always do the same thing that you did, then there's no point.
For anyone having trouble with combos, check out the webpage, http://onslaught.playr.co.uk/about.html.
Personally, I like the nuke combo, especially with a few tazer towers set out in front of it. That slows down the enemies enough to group them up, allowing the nukes to take them all out at once.
Welder is right, the framerate inconsistency makes the game massively harder on an older computer. I'm playing the game on a new computer now and I can run across the death fields twice as fast as before.
I'm back to thinking that the training is useless. I'm not strong enough to beat the boss (Galiant the Paladin) but the training enemies are such a joke that I only get 2 xp for them.
Level 8 is a huge difficulty jump. I don't think the earlier levels prepared me for what I'm supposed to do. Trying to do anything during a fight is problematic, the menu keeps resetting.