{
 "id": "62-heat-sink",
 "name": "Heat sink with 15 fins",
 "description": "60x50x5 base; one 1.5x50 fin 25 tall at x=2; rectangular pattern x15 @4 mm.",
 "exercises": [
  "extrude_join",
  "rectangular_pattern",
  "many_faces",
  "realistic"
 ],
 "units": {
  "length": "mm",
  "angle": "deg",
  "area": "mm2",
  "volume": "mm3"
 },
 "conventions": {
  "world": "right-handed; Z up. XY/XZ/YZ are the origin planes.",
  "sketch_frame": "sketch-local 2D coords; world = plane.origin + x*plane.x_dir + y*plane.y_dir (origin in mm). Profile 'loops' list sketch entity ids.",
  "point_refs": "'<id>.start' / '<id>.end' / '<id>.center' reuse (share) that existing sketch point; 'at' is its position when referenced.",
  "extrude_direction": "positive = along sketch plane normal unless stated",
  "selections": "selected faces/edges carry 'point': a world-space point on the face / the edge's parametric midpoint; pick the nearest face/edge to it."
 },
 "parameters": [],
 "features": [
  {
   "op": "sketch",
   "name": "Base_sketch",
   "plane": {
    "ref": "XY",
    "origin": [
     0.0,
     0.0,
     0.0
    ],
    "x_dir": [
     1.0,
     0.0,
     0.0
    ],
    "y_dir": [
     0.0,
     1.0,
     0.0
    ],
    "normal": [
     0.0,
     0.0,
     1.0
    ]
   },
   "entities": [
    {
     "type": "line",
     "start": {
      "at": [
       0,
       0
      ]
     },
     "end": {
      "at": [
       60,
       0
      ]
     },
     "id": "l1"
    },
    {
     "type": "line",
     "start": {
      "ref": "l1.end",
      "at": [
       60.0,
       0.0
      ]
     },
     "end": {
      "at": [
       60,
       50
      ]
     },
     "id": "l2"
    },
    {
     "type": "line",
     "start": {
      "ref": "l2.end",
      "at": [
       60.0,
       50.0
      ]
     },
     "end": {
      "at": [
       0,
       50
      ]
     },
     "id": "l3"
    },
    {
     "type": "line",
     "start": {
      "ref": "l3.end",
      "at": [
       0.0,
       50.0
      ]
     },
     "end": {
      "ref": "l1.start",
      "at": [
       0.0,
       0.0
      ]
     },
     "id": "l4"
    }
   ],
   "constraints": [],
   "dimensions": []
  },
  {
   "op": "extrude",
   "name": "Base",
   "operation": "new",
   "profiles": [
    {
     "sketch": "Base_sketch",
     "loops": [
      {
       "outer": true,
       "curves": [
        "l1",
        "l2",
        "l3",
        "l4"
       ]
      }
     ]
    }
   ],
   "extent": {
    "type": "distance",
    "distance": 5,
    "direction": "positive"
   },
   "result_bodies": [
    "HeatSink"
   ]
  },
  {
   "op": "construction_plane",
   "name": "BaseTop",
   "method": "offset",
   "base": "XY",
   "offset": 5
  },
  {
   "op": "sketch",
   "name": "Fin",
   "plane": {
    "ref": "construction plane BaseTop (z=5)",
    "origin": [
     0.0,
     0.0,
     5.0
    ],
    "x_dir": [
     1.0,
     0.0,
     0.0
    ],
    "y_dir": [
     0.0,
     1.0,
     0.0
    ],
    "normal": [
     0.0,
     0.0,
     1.0
    ]
   },
   "entities": [
    {
     "type": "line",
     "start": {
      "at": [
       2,
       0
      ]
     },
     "end": {
      "at": [
       3.5,
       0
      ]
     },
     "id": "l1"
    },
    {
     "type": "line",
     "start": {
      "ref": "l1.end",
      "at": [
       3.5,
       0.0
      ]
     },
     "end": {
      "at": [
       3.5,
       50
      ]
     },
     "id": "l2"
    },
    {
     "type": "line",
     "start": {
      "ref": "l2.end",
      "at": [
       3.5,
       50.0
      ]
     },
     "end": {
      "at": [
       2,
       50
      ]
     },
     "id": "l3"
    },
    {
     "type": "line",
     "start": {
      "ref": "l3.end",
      "at": [
       2.0,
       50.0
      ]
     },
     "end": {
      "ref": "l1.start",
      "at": [
       2.0,
       0.0
      ]
     },
     "id": "l4"
    }
   ],
   "constraints": [],
   "dimensions": []
  },
  {
   "op": "extrude",
   "name": "Fin",
   "operation": "join",
   "profiles": [
    {
     "sketch": "Fin",
     "loops": [
      {
       "outer": true,
       "curves": [
        "l1",
        "l2",
        "l3",
        "l4"
       ]
      }
     ]
    }
   ],
   "extent": {
    "type": "distance",
    "distance": 25,
    "direction": "positive"
   },
   "result_bodies": [
    "HeatSink"
   ]
  },
  {
   "op": "rectangular_pattern",
   "name": "FinPattern",
   "pattern_of": "features",
   "features": [
    "Fin (1)"
   ],
   "direction1": {
    "axis": [
     1,
     0,
     0
    ],
    "count": 15,
    "spacing": 4
   },
   "distance_type": "spacing (distance between instances)"
  }
 ]
}