Released in 2003, Hasbro's Built to Rule is a line of building block sets that, when assembled, resemble toys from some of Hasbro's other toylines: G.I. Joe, Tonka, and Transformers. The building blocks are compatible with the Lego or Mega Blocks brands of building blocks.
The Transformers Built to Rule toyline consisted of an Armada line, which received a very wide public release, and a short-lived Energon line, which only had a limited, test market release initially in and around Cincinnati, Ohio. The sets later filtered out into some "Tuesday Morning", "Ollie's", and "T. J. Maxx" chain stores at drastically dropped prices. The entire line seemed to perform poorly, so it was dropped in its entirety in 2004.
Some fans posit that had the Transformers series followed the lead of the G.I. Joe and Tonka sets, with a standard large-character/vehicle block set but including a "normal" figure, for example a Mini-Con compatible with the normal Armada line but with a few BTR-style construction pegs (the Joe sets had normal Joe figures with newly-sculpted forearms and lower legs with BTR pegs to attach parts to), it might have done a little better, especially considering the Mini-Cons' popularity with kids. But since the entire branch was cancelled after a year, it's hard to say so with any confidence.
There are some significant differences between the Armada and Energon sets, though both are based on the same basic premise. Each Transformers kit is centered around a "Trans-Skeleton", a very simple humanoid body that folds up for vehicle mode without disassembly. From there, extra parts are added to the Trans-Skeleton for either mode.
For Armada, the Trans-Skeleton was a very broad, flat solid plate with thin, stick-like limbs attached to it. This led to very awkward-looking robot modes, especially at the smaller sizes. Each of these sets also came with an incredibly simplistic "Mini-Con" partner kit that did have a more dedicated "Powerlinx" connector than the standard construction pegs, though these are a bit too thin to be used as attachment points for regular Mini-Cons (they stay, sort of, but it's a very loose connection).
The structure of the Trans-Skeleton was changed for a pair of small sets originally intended to be the Mini-Cons Ramjet and Rollout for the Armada series; a much more solid skeleton with larger, blockier limbs. These two kits were never released, but were altered to become the Energon characters Skyblast and Inferno (at a larger price point to boot). The rest of the Energon Built To Rule kits followed this style of Trans-Skeleton, leading to much more solid, stable and sturdy-looking robot modes.
- Optimus Prime with Sparkplug
- Red Alert with Longarm
- Hot Shot with Jolt
- Jetfire with Comettor
- Smokescreen with Liftor
- Thrust (Armada) with Inferno (Armada)
- Megatron & Cyclonus with Leader-1 & Crumplezone
- Starscream with Swindle
- Demolishor with Blackout
- Thundercracker with Zapmaster
- Night Attack Demolishor with Blackout