It has been nearly 15 years since this flash game came out, and having played it again recently, I decided I'd give a more proper review, especially when I noticed a bunch of the more constructive reviews tended to be rated down for some reason.
Balloon Duel was a marvel of its time, with a lot of innovations such as its very heavy customization and ability to play custom music, and it grants players a chance to play a re-imagined 1v1 duel style of the original NES Balloon Fight. I still remember both of these childhood games fondly.
Unfortunately, the game hasn't aged well. Obviously, changes in technology have rendered aspects of the game unable to function as it originally did, such as being unable to play music or the blinking effect on respawning being kinda screwed up(making you invisible for a while). However that's not fair to the game, nor is it the focus of my review.
The singleplayer will be my main focus of my review, since that is what the majority of players would have experienced playing this. While I can't speak for the experience of sharing a keyboard to compete against one another in this game specifically, I can say that the singleplayer experience against the AI and the rank system are the weakest parts of the game, and it all comes from a large chain of factors that make it a poor experience.
There is no real incentive to stop players from simply staying at the very top of the arena. Due to the nature of the game, you'd almost always want to have the high ground so that you can pop the enemy but not vice-versa. It also feels like gravity in this game seems a bit higher than the original NES game, so that means you need to flap quite a lot more to stay afloat. And that is where the lack of platforms become a problem - players have to constantly flap or die, there is no ground to rest on and no place to hide under from someone from above.
Understandably, platforms were not added due to difficulties with making the AI. However, the AI is able to flap faster you can ever mash and can somehow always gain the high ground... and tend to just stay there. This devolves into a game where you mash flap as fast as you can, staying at the top of the arena and ramming each other, all to take the chance that your enemy gets pushed just enough by the recoil to get their balloons popped. Nothing was done to discourage this kind of behavior the same way you could fall off the map or get eaten by fish if you stay too close to the bottom.
As a result of all these factors, the optimal strategy is to just stick to using the basic Autoflap you have at the start of the game and constantly stay at the top of the map - it is the easiest way to stay afloat without putting huge physical stress on your fingers. The only time you'd have difficulty pulling this off is at the beginning of each match, where the AI would immediately fly to the top while players still have to react to having left click "Start", moving their mouse cursor away from the screen, and then move their fingers into position on the keyboard, and autoflap doesn't work until the battery is fully charged.
This strategy is so effective that you can beat most Rank 100 AI(depending on their special weapon) consistently and easily. It also doesn't help that you can just keep re-rolling your opponent until you get one with a "good" special weapon to farm, and then stick to that opponent for the rest of the game. I'll get to the special weapons later.
With that in mind, let's talk about the in-game economy and rank system. Customizing your character costs in-game currency and is also needed to buy more weapons, and I think that's perfectly fine. What isn't fine is the rank system and how currency is linked to it. You gain rank by beating an opponent of a higher ranking than you, and in turn the paycheck you get at the end of each fight increases as your rank increases(the rank is adjusted before the paycheck). The problem is, your rank will decrease if you deal with a lower ranked enemy(which you may normally want to do if you find rank 100 a bit too stressful to deviate from the optimal autoflap strat), and this in turn reduces your paycheck and makes you lose access to the bonus game modes which require a high rank to unlock!
Its clear that the intention of the author is to encourage players to get better at the game and not downgrade, but in practice this ultimately reduces the enjoyment of the game and forces players to stick to a safe strat to stay in the high ranks for a bigger paycheck. A far better approach is to make the paycheck based on the rank of the opponent rather than your own rank, and the bonus gamemodes shouldn't be re-locked just because you lost rank. I'd also like to mention that you can deliberately quit back to menu by pressing ESC if you feel you did poorly, rolled a bad opponent and don't want to lose rank, though it does also mean you won't earn a paycheck, so kudos for not allowing that exploit to happen.
That brings me to the special weapons, which is the most awesome aspect and biggest selling point of the gameplay. It enhances the sense of unique customization, creates interesting matchups in an otherwise stale game and allow tactics that would otherwise not be possible to shine. They're not necessarily well-balanced, but they are fun and fresh to the game. Therefore, it is a huge letdown when I found out that the bonus gamemodes(especially the Rank 100 soldier training) do not allow you to take your special weapons with you. There is even a weapon (EMP) that specifically stops other people from using their special weapon. WHY?! That's the best part of the game and you're stopping people from using them? Not a wise decision.
That leaves with me some minor miscellaneous things I think is worth pointing out.
* Generally, the shops' preview options could be a bit better. For instance, you will need to buy the weapon and actually use it in practice or the arena to actually have a proper idea of what it does, and you can't preview your full character's appearance if you're updating the head or face.
* The game also doesn't spell out the weapons that the enemy is using, which can be annoying if they are using some of the admittedly similar-looking backpacks of certain weapons, which are further obstructed by their clothes.
* The text speed is generally a bit too slow, it'd work better if players could speed it up without skipping to the next wall of text.
* The AI tends to hover above you when you fall off, so that they can immediately push you back down and kill you.
* Players are advised to change their controls, and in a way that emulates an NES controller - left/right on the left, and flap/weapon on the right of your keyboard.
Despite all the criticisms I have hurled against the game, I did greatly enjoy this as a kid and spent hours upon hours on it. It came at the right time, when teens wanted to relive the nostalgia of Balloon Fight in a time when Flash animations/games were at their peak. While I think that the nostalgia and cool factor of having special weapons/customization have given us rose-tinted glasses on how good game actually was in terms of gameplay, I think what's more important is that this game gave us a great experience and memory we'd never forget. Looking at it purely in terms of gameplay, I would have given this a 3.5 or even a 3, but there is a reason why this game is a classic and why I ultimately gave this a 4.
Thank you Mousekliks, for making this great classic of a flash game.