Scrapforge

Everything that comes at you is also the thing you build with.

Scrap falls into the forge. Two of the same kind that touch become the next one up, and what comes out of the forge is bolted onto the line that is keeping the horde off you. Fuse badly and you are holding a wall of junk; fuse well and the wall shoots back.

• Merging that feeds a defence rather than merging for its own sake — every fusion is a decision about what the next thirty seconds look like.
• A workshop that keeps what you learned. What you install stays installed between runs.
• The horde reads the field. It comes for the weakest part of what you built, which is usually the part you were proudest of.

Plays in the browser. Nothing to install, nothing to sign up for.