One nice thing about Unity is its ecosystem. In the Unity Asset Store you can find a wide variety of systems and engines that help a lot.
One of those is Redbee's 2.5D Platformer Engine. Redbee's 2.5D Platformer Engine is a system designed to help you make sidescroller platformers that use 3D graphics.
It's called 2.5D because, while the graphics are 3D, you can only move in two dimensions. I recently got this engine because I plan to make a sidescroller platformer soon, and it looked like it would fit my needs pretty well.
Redbee's engine offers the basic functionality that you would expect from a sidescroller engine, as well as some extra nice features (more about that later).
The character is able to move left and right, jump, get on moving platforms, and also has a double jump. All of these, with the exception of a double jump, are the basic things you'd expect from a sidescroller engine.
However, this engine offers a few more transversal features that can allow for interesting games. One of those extra features is the ability to perform a wall jump, and another one is the ability to slide down walls slowly.
The creator also added different world interactions.
For example, you can create a dynamic rope so your character can swing left and right, to gain momentum for a jump. The avatar can also grab on to edges, Prince of Persia style, step on pressure pads that can be used for scripted objects (as well as push objects onto those pressure pads), and also grab keys that can be used to open doors.
All these features can really help you make interesting games with a variety of gameplay scenarios.
The 2.5D Platformer Engine also includes a combat system. Your avatar can perform attacks and combos, and you can setup the damage amount for each attack. The engine also includes a computer-controlled enemy that can perform your same moves, and can attack you.
One thing I have to admit is that the enemy AI can perform actions that will look really dumb. For example, if you get on the other side of a tall wall, the AI will try to jump that wall non-stop, something that ends up looking a little dumb.
A really nice feature is the addition of “turns.” In the engine you can configure triggers that will make the character “turn” along a curve. This is a very nice visual effect and allows for interesting level designs that are no longer limited to 2D.
I have to say the package has a really big flaw, though. The flaw is not in the package itself, but rather in the documentation. The documentation is extremely lacking, since it barely explains some things without going into details. At the end, you end up learning more about how to use the system by exploring the sample scene than by reading the manual.
Another big flaw to me is the lack of actual Unity prefabs.
I don't expect a fancy prefab creation system like the one in Adventure Creator (although it would be awesome), but at least being able to assemble levels from scratch using the prefab triggers, platforms and such would be great (for example, the “turns” prefab or the “kill volume” prefab).
Instead, you have to create all those manually. I know you just need to create the prefabs yourself, but that doesn't change the fact that the creator could have just added those to the pack to begin with.
Redbee's 2.5D Platformer Engine is, in general, a really good tool for Unity. However, lack of documentation and the fact that you will have to manually setup things makes you waste some time when you first start using it.
Redbee's 2.5D Platformer Engine: https://assetstore.unity.com/packages/templates/systems/2-5d-platformer-engine-93500