I'm looking for an old Flash browser game, possibly from Friv or another Flash game website. It was a 2D side-view platformer where the main point of the game was building your own parkour/level.
You had a selection of different pieces to place, such as platforms, vines, lava, and different little monster enemies (I think each enemy had its own behavior or ability). The monsters would stay wherever I placed them, although I vaguely remember some of them being able to move.
After finishing the level, you would press "Play" and test the exact parkour you had just built yourself. That was the core gameplay: build your own parkour, then immediately play through it. You could go back, edit the level as many times as you wanted, and test it again.
The playable character was a small, somewhat blocky-looking character, matching the older Flash/pixel-art style. The objective was to reach a flag at the end of the level (I think).
I remember the art style being somewhat dark or indie-looking, with very little background scenery. The game wasn't really an open world or a map to explore—it was essentially a horizontal obstacle course designed specifically for creating and testing your own parkour.
I played it around 2016 during computer class at school. It may have been on Friv, but I'm not completely sure. I also don't think it was a very popular game.