Def a solid 4.5/5. Nothing that I would call difficult, just some of the puzzles were far too fidgety, but I'd say it's definitely more of a design flaw than a bug. It would get a 15/10 on the usual idle game garbage flowing through Kongregate these days though.
I get the feeling this game tries really hard, yet it falls short. Obvious improvements would be upgrades such as more bullets/faster fire rate, which HatHelper291 has already pointed out. Other upgrades that would help tremendously would be a movement speed modifier, specific spell upgrades such as the fireball could be upgraded to be larger, the duration of ice shards could be longer and more poison darts with possible infection of other creatures by affected initial creatures. Also, the pets are largely kind of pointless, allow them to have skill trees as well maybe 2 different paths for each depending on if you want them to be more offensive or defensive. Give more information of upgrades and actual initial numbers, the information given does not give really information at all other than click here to advance this skill 1 bar.. Ok, what does this go from-to? The game is almost there, but it just isn't polished.
Major bug with the game. If you upgrade Ballista to 3 stars, it starts the next round as a Cannon. When you fire, even when you hit max, it only launches you 4 ft. The only way to work around this is to either have upgraded the dice so you get paid every time you launch at max to be able to pay the $2500 for the canon's first star, or to us your rocket immediately after you launch. In any case, it's a pretty huge bug.
Time attack with 2 allies is a the most assholish thing about this game since the ai pathfinding has them moving from 1 side of the map to the next instead of just focusing on more localized groups of enemies.
After the level reloads, they need to pause until a key is pressed to signal the player is moving. Some levels are terrible like that, but I supposed that's in the a**holish nature of the game by design?
just keep combining, it'll freeze the action for a moment, but it'll seemingly take the weakest of combined mini ninjas and throw them back into the larger pile and throw the strongest one out by itself, it'll keep replenishing the health meter of the "weaker" units. Just keep combining the units as a large group, the game will do the rest. I don't know if this is as much of a cheat as it is just using the games engine to your benefit.
Some games are better off not remade. Just duck to slide.. Oh.. Can't do that, oh yeah, this game is really old before pixels knew how to slide.. Wait a sec.. Mega Man could slide in the early 90's.. N stands for Nevermind these days.
 "Labyrneath II"){kind=icon}
 "Brave Shorties 2"){kind=icon}
 "Temple of the Four Serpents"){kind=icon}
 "Get A Little Gold"){kind=icon}
 "Medieval Angel 5 -My Destiny- (Part 1)"){kind=icon}
 "Aqua Boy"){kind=icon}
 "Sentry Knight Conquest"){kind=icon}
 "Strikeforce Kitty 2"){kind=icon}
 "Go Go Goblin 2"){kind=icon}
 "Madmen Racing"){kind=icon}
 "Mighty Knight"){kind=icon}
 "Ultimate Monster Mayhem"){kind=icon}
 "Golden Scarabaeus"){kind=icon}
 "Pause Ahead"){kind=icon}
 "Pocket Ninja"){kind=icon}
 "Bloons Super Monkey 2"){kind=icon}
 "PicTune"){kind=icon}
 "Disaster Will Strike 2"){kind=icon}
 "The King's League: Odyssey"){kind=icon}
 "N (Official Web Version)"){kind=icon}