There's an art to making an upgrade game. You want the player to feel as though they have multiple viable paths to victory, but that their choices matter.
Ideally, this is achieved not by perfectly balancing all the different upgrades, but by making each upgrade situational. Whether it's Cookier Clicker, Burrito Bison, or ROBOKILL, you want the player to be constantly discovering new and clever ways of stretching their resources... of tweaking things so that they can draw juuuuuuust a little bit more power out of their arsenal, and occasionally discovering game-breakers that make them feel smart.
None of this ever happens in Free Fred, and it all stems from the decision to make it a 2D game in which the player is completely immobile.
You can't move left or right to dodge bombs. You can't jump or otherwise avoid damage. This means that it's basically a stationary player-controlled turret defense game... except that instead of surviving nights or beating levels, the game is structured as one long level. This means you need to fail and fail and fail over and over again in order to succeed. There is no progress, other than monetarily. You just start the level over again from the beginning.
In a sense, side-view perspective gives the combat in Free Fred slightly more variety than a typical top-down player-controlled turret game. The enemies approach by sea and sky, and your upgrade paths include dedicated "lane coverage" for one or both of these. In theory, you could upgrade either Torpedoes or Homing Missiles to lock down one of those lanes, allowing you to focus on the other with your turrets.
In practice, however, homing missiles are too slow to actually do anything when the screen starts to fill with fast-moving helicopters, and the sea is completely linear in a side-scroller, so it quickly becomes a huge mass of overlapping battleships and various flavors of sea mines. In other words, the homing missiles typically either don't hit anything, or else waste a lot of your time and then hit a random target, while the torpedoes just do extra damage to whatever's queued up in the sea lane.
A skilled player will take no damage at all, until he hits the point in the game where more upgrades are needed, and then he will start taking very heavy damage very quickly. Once you unlock the third ship, the medic helicopter provides a false sense of security. It won't last. You still recognize the wall when you hit it. The only way to make it through is to hammer the enemy with overwhelming firepower, and this is generally only possible once you have near max upgrades.
I was able to beat the game with all but one HP upgrades, zero homing missile upgrades, and everything else maxed. Then I maxed out the homing missiles, just to see what they do. They remain awkward, slow, and clumsy, frequently swerving to avoid new enemies and taking down enemies up to 30 seconds after I would have with the turret. Target prioritization also makes no sense-- they sure don't lock onto whatever heat signature's the closest, the way homing missiles would in real life.
And speaking of homing missiles, why can't I shoot these fuckers down? I wouldn't mind, except that some battleships and submarines fire homing missiles that you NEED to shoot down, and they're identical in shape and behavior to the ones you can't shoot down.
Coding is well-done, with no slow-downs, even when things got busy, and even after long gameplay sessions. Some gameplay design choices seem questionable, and the decision to inexplicably use the plot of Free Willy as a franking device feels exploitative, hackneyed, and out-of-date, all at the same time. Graphics are okay. I would say I appreciate the Dr. Strangelove reference, but upon closer inspection of the guy riding the bomb, I doubt it was intentional.
3 out of 5 about covers it. I would have given it a 2, but the last boss did something new and slightly more complex, and I appreciate the solid stability of the coding. I suppose you probably can't expect much from a game whose only reason for existing is to make you go to a different website, but other, better upgradable turret games have taught us to expect better.