This puzzle is part of the Monthly Topic Challenge #13: Variety Slitherlinks.
Adding a bit of colour to enhance the loopy goodness of a traditional Slitherlink.
- Draw a single, non-intersecting loop that only consists of horizontal and vertical segments between the dots.
- Numbers inside a cell indicate how many of the edges of that cell are part of the loop.
- Shade the interior of the loop so that every cell is part of an L, I, T, or S tetromino.
- No 2×2 group of cells can be entirely shaded.
- When two tetrominoes share an edge, they must not be of the same type (L, I, T, or S), regardless of rotations or reflections.
Should be solvable by hand with no guessing/backtracking.
Penpa link (If you want the Penpa automated checker to work, Use Green for the loop, and (DG, GR, LG, BK) for shading.)