diff --git a/README.md b/README.md
index 1612ea9..4fe7908 100644
--- a/README.md
+++ b/README.md
@@ -23,12 +23,25 @@ test = Engine3D([[1, 1, 1], [0, 0, 0], [2, 2, 2]], [[0, 1, 2]]) # this will crea
 test = Engine3D([[1, 1, 1], [0, 0, 0], [2, 2, 2]], [[0, 1, 2, "green"]]) # you can also change the color of the triangle (the default is green)
 ```
 
-From your code, you can modify the display using the writePoints, writeTriangles, rotate, clear and render methods.
+You can also define a list of folds that would be used to animate a multi-step folding.
+Each folding step is itself composed of simultaneously done line folds.
+Each line fold is defined by it's angle in degreee, two vertices that defines an oriented axe and a list of concerned vertices.
+
+```Python
+vertices = [[-1, -1, 1], [-1, 1, 0], [1, -1, .5], [-1, -1, -.5]]
+faces = [[0, 1, 2, "green"], [1, 2, 3, "red"]]
+folds = [[(45, 1, 2, [3])]]
+test = Engine3D(vertices, faces, folds)
+```
+
+From your code, you can modify the display using the writePoints, writeTriangles, rotate, free_rotate, part_free_rotate, clear and render methods.
 
 ```Python
 test.writePoints([[3, 3, 3], [0, 0, 0], [2, 2, 2]]) # change the points
 test.writeTriangles([[2, 1, 0, "blue"]]) # the order of the points does not matter
 test.rotate("y", 45) # rotate the object 45 degrees around the y axis
+test.free_rotate(45, 1, 2) # rotate the object 45 degrees around vertices[1]vertices[2] axis
+test.part_free_rotate(45, 1, 2, [3, 4]) # rotate vertices[3] and vertices[4] 45 degrees around (vertices[1],vertices[2]) axis
 test.clear() # clear the display
 test.render() # update the image
 ```
@@ -39,6 +52,7 @@ You can also use the following keys to interact with the display.
 2. Up arrow -> Zoom in
 3. Down arrow -> Zoom out
 4. w, a, s, d -> Move the view up, left, down or right
+5. n, p -> Animate the next or previous fold
 
 The module now also allows you to move points on the model (this is still a work in progress)
 
@@ -48,4 +62,5 @@ The module now also allows you to move points on the model (this is still a work
 
 ---
 
-If you would like to help me improve this project, you can contact me at code@henryhaefliger.com
+Initial code: code@henryhaefliger.com
+Folding and free rotation axis code: miq75@free.fr
diff --git a/__pycache__/graphics.cpython-37.pyc b/__pycache__/graphics.cpython-37.pyc
deleted file mode 100644
index b32dfca..0000000
Binary files a/__pycache__/graphics.cpython-37.pyc and /dev/null differ
diff --git a/coords/GalleonT.txt b/coords/GalleonP.txt
similarity index 100%
rename from coords/GalleonT.txt
rename to coords/GalleonP.txt
diff --git a/coords/SharkP.txt b/coords/SharkP.txt
new file mode 100644
index 0000000..3d53ede
--- /dev/null
+++ b/coords/SharkP.txt
@@ -0,0 +1,734 @@
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diff --git a/coords/SharkT.txt b/coords/SharkT.txt
deleted file mode 100644
index a852979..0000000
--- a/coords/SharkT.txt
+++ /dev/null
@@ -1,734 +0,0 @@
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-3 156 210 211 
-3 187 156 211 
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-3 213 214 215 
-3 216 213 215 
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-3 230 231 233 
-3 230 233 232 
-3 187 229 234 
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-3 187 218 223 
-3 187 212 218 
-3 206 208 186 
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-3 194 235 236 
-3 237 235 194 
-3 237 194 193 
-3 238 237 193 
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-3 243 240 242 
-3 243 242 244 
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-3 246 236 241 
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-3 248 246 247 
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-3 251 252 236 
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-3 256 260 261 
-3 256 261 262 
-3 262 261 257 
-3 262 257 259 
-3 260 256 191 
-3 256 250 191 
-3 250 245 191 
-3 245 239 191 
-3 194 236 258 
-3 236 252 258 
-3 204 205 263 
-3 204 263 264 
-3 265 204 264 
-3 265 264 266 
-3 267 265 266 
-3 267 266 268 
-3 140 267 268 
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-3 269 142 143 
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-3 273 271 272 
-3 273 272 274 
-3 275 273 274 
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-3 277 278 271 
-3 277 271 273 
-3 278 260 269 
-3 278 269 271 
-3 260 279 142 
-3 260 142 269 
-3 279 280 139 
-3 279 139 142 
-3 280 281 140 
-3 280 140 139 
-3 281 234 267 
-3 281 267 140 
-3 234 282 265 
-3 234 265 267 
-3 282 202 204 
-3 282 204 265 
-3 188 187 234 
-3 188 234 281 
-3 189 188 281 
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-3 191 190 279 
-3 191 279 260 
-3 235 241 236 
-3 214 209 208 
-3 273 283 277 
-3 275 283 273 
-3 258 277 283 
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-3 285 286 287 
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-3 291 288 290 
-3 291 290 292 
-3 293 294 295 
-3 296 297 298 
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-3 301 302 303 
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-3 305 301 304 
-3 276 274 306 
-3 276 306 307 
-3 274 272 308 
-3 274 308 306 
-3 272 270 309 
-3 272 309 308 
-3 270 143 310 
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-3 143 136 311 
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-3 136 141 312 
-3 136 312 311 
-3 141 268 313 
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-3 268 266 314 
-3 268 314 313 
-3 266 264 315 
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-3 264 263 316 
-3 264 316 315 
-3 307 306 317 
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-3 306 319 317 
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-3 308 320 319 
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-3 309 321 320 
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-3 311 323 322 
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-3 318 337 338 
-3 339 340 129 
-3 339 129 133 
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-3 342 132 131 
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-3 343 128 132 
-3 302 344 125 
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-3 346 122 123 
-3 347 348 126 
-3 347 126 122 
-3 329 328 348 
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-3 334 302 343 
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-3 338 340 339 
-3 116 126 349 
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-3 115 350 116 
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-3 351 353 354 
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-3 352 173 353 
-3 184 355 356 
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-3 358 360 362 
-3 358 362 363 
-3 356 358 363 
-3 356 363 364 
-3 185 356 364 
-3 185 364 186 
-3 353 173 194 
-3 353 194 365 
-3 354 353 365 
-3 354 365 361 
-3 366 367 352 
-3 366 352 351 
-3 367 40 172 
-3 367 172 352 
-3 7 368 355 
-3 7 355 184 
-3 368 369 357 
-3 368 357 355 
-3 369 370 359 
-3 369 359 357 
-3 370 366 351 
-3 370 351 359 
-3 367 366 370 
-3 367 370 369 
-3 367 369 368 
-3 371 372 373 
-3 206 373 372 
-3 205 372 371 
-3 374 375 376 
-3 374 376 377 
-3 186 364 373 
-3 186 373 206 
-3 378 377 376 
-3 378 376 379 
-3 371 378 379 
-3 371 379 380 
-3 205 371 380 
-3 205 380 263 
-3 381 275 276 
-3 381 276 382 
-3 374 381 382 
-3 374 382 375 
-3 383 384 381 
-3 383 381 374 
-3 373 385 378 
-3 373 378 371 
-3 385 386 377 
-3 385 377 378 
-3 386 383 374 
-3 386 374 377 
-3 362 361 383 
-3 362 383 386 
-3 363 362 386 
-3 363 386 385 
-3 364 363 385 
-3 364 385 373 
-3 365 194 258 
-3 365 258 384 
-3 361 365 384 
-3 361 384 383 
-3 384 387 381 
-3 381 387 275 
-3 387 384 258 
-3 98 172 23 
-3 114 42 184 
-3 375 382 388 
-3 375 388 389 
-3 382 276 307 
-3 382 307 388 
-3 263 380 390 
-3 263 390 316 
-3 380 379 391 
-3 380 391 390 
-3 379 376 392 
-3 379 392 391 
-3 376 375 389 
-3 376 389 392 
-3 389 388 393 
-3 389 393 394 
-3 388 307 318 
-3 388 318 393 
-3 316 390 395 
-3 316 395 327 
-3 390 391 396 
-3 390 396 395 
-3 391 392 397 
-3 391 397 396 
-3 392 389 394 
-3 392 394 397 
-3 397 394 398 
-3 397 398 399 
-3 396 397 399 
-3 396 399 400 
-3 395 396 400 
-3 395 400 401 
-3 327 395 401 
-3 327 401 328 
-3 393 318 338 
-3 393 338 402 
-3 394 393 402 
-3 394 402 398 
-3 403 404 350 
-3 403 350 115 
-3 404 339 133 
-3 404 133 350 
-3 348 405 349 
-3 348 349 126 
-3 405 406 120 
-3 405 120 349 
-3 406 407 119 
-3 406 119 120 
-3 407 403 115 
-3 407 115 119 
-3 399 398 403 
-3 399 403 407 
-3 400 399 407 
-3 400 407 406 
-3 401 400 406 
-3 401 406 405 
-3 328 401 405 
-3 328 405 348 
-3 402 338 339 
-3 402 339 404 
-3 398 402 404 
-3 398 404 403 
-3 127 408 128 
-3 127 409 408 
-3 127 410 409 
-3 127 411 410 
-3 127 412 411 
-3 127 413 412 
-3 127 414 413 
-3 127 121 414 
-3 128 408 134 
-3 408 409 134 
-3 409 410 134 
-3 410 411 134 
-3 411 412 134 
-3 412 413 134 
-3 413 414 134 
-3 414 121 134 
-3 415 139 135 
-3 416 415 135 
-3 417 416 135 
-3 418 417 135 
-3 419 418 135 
-3 420 419 135 
-3 421 420 135 
-3 422 421 135 
-3 423 422 135 
-3 424 423 135 
-3 135 137 424 
-3 138 139 415 
-3 138 415 416 
-3 138 416 417 
-3 138 417 418 
-3 138 418 419 
-3 138 419 420 
-3 138 420 421 
-3 138 421 422 
-3 138 422 423 
-3 138 423 424 
-3 424 137 138 
-3 155 425 144 
-3 425 426 144 
-3 426 427 145 
-3 427 428 145 
-3 428 429 152 
-3 429 430 152 
-3 430 431 153 
-3 431 432 153 
-3 432 433 149 
-3 433 434 149 
-3 434 154 148 
-3 144 426 145 
-3 145 428 152 
-3 152 430 153 
-3 153 432 149 
-3 149 434 148 
-3 155 144 148 
-3 162 435 168 
-3 162 436 435 
-3 161 437 436 
-3 161 438 437 
-3 166 439 438 
-3 166 440 439 
-3 167 441 440 
-3 167 442 441 
-3 165 443 442 
-3 165 444 443 
-3 164 169 444 
-3 161 436 162 
-3 166 438 161 
-3 167 440 166 
-3 165 442 167 
-3 164 444 165 
-3 164 162 168 
-3 160 445 446 
-3 146 445 160 
-3 146 447 445 
-3 146 172 447 
-3 160 446 184 
-3 40 367 368 
-3 40 368 7 
-3 445 447 446 
-3 40 7 184 
-3 40 184 172 
-3 184 446 447 
-3 184 447 172 
-3 233 231 202 
-3 233 202 282 
-3 233 282 234 
-3 227 232 229 
-3 226 225 230 
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-3 222 224 228 
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-3 211 216 212 
-3 211 210 213 
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-3 231 206 202 
-3 278 277 257 
-3 278 257 261 
-3 260 278 261 
-3 256 262 255 
-3 259 252 251 
-3 255 262 259 
-3 255 259 251 
-3 254 253 246 
-3 254 246 248 
-3 253 236 246 
-3 245 249 243 
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-3 249 240 243 
-3 247 241 240 
-3 242 235 237 
-3 250 254 248 
-3 239 244 238 
-3 244 242 237 
-3 244 237 238 
-3 277 258 257 
-3 448 449 372 
-3 449 206 372 
-3 450 448 372 
-3 451 450 372 
-3 452 451 372 
-3 453 452 372 
-3 454 453 372 
-3 455 454 372 
-3 456 455 372 
-3 457 456 372 
-3 372 205 207 
-3 372 207 457 
-3 457 207 203 
-3 203 456 457 
-3 203 455 456 
-3 203 454 455 
-3 203 453 454 
-3 203 452 453 
-3 203 451 452 
-3 203 450 451 
-3 203 448 450 
-3 203 449 448 
-3 203 206 449 
-3 430 429 428 
-3 430 428 427 
-3 430 427 426 
-3 430 426 425 
-3 430 425 155 
-3 430 155 154 
-3 430 154 434 
-3 430 434 433 
-3 430 433 432 
-3 430 432 431 
-3 441 442 443 
-3 441 443 444 
-3 441 444 169 
-3 441 169 168 
-3 441 168 435 
-3 441 435 436 
-3 441 436 437 
-3 441 437 438 
-3 441 438 439 
-3 441 439 440 
-3 458 284 387 
-3 284 275 387 
-3 387 459 458 
-3 387 460 459 
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-3 387 462 461 
-3 387 463 462 
-3 387 464 463 
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-3 387 466 465 
-3 387 467 466 
-3 387 258 467 
-3 283 284 458 
-3 458 459 283 
-3 459 460 283 
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-3 463 464 283 
-3 464 465 283 
-3 465 466 283 
-3 466 467 283 
-3 467 258 283 
\ No newline at end of file
diff --git a/cubeExample.py b/cubeExample.py
deleted file mode 100644
index 6123e64..0000000
--- a/cubeExample.py
+++ /dev/null
@@ -1,20 +0,0 @@
-### Cube ###
-
-import graphics.engine
-
-points = [[-1,-1,-1],[-1,-1,1],[-1,1,1],[-1,1,-1],[1,-1,-1],[1,-1,1],[1,1,1],[1,1,-1]]
-triangles = [[0,1,2],[0,2,3],[2,3,7],[2,7,6],[1,2,5],[2,5,6],[0,1,4],[1,4,5],[4,5,6],[4,6,7],[3,7,4],[4,3,0]]
-
-test = graphics.engine.Engine3D(points, triangles, title='Cube')
-
-def animation():
-    test.clear()
-    test.rotate('y', 0.1)
-    test.rotate('x', 0.1)
-    test.render()
-    test.screen.after(1, animation)
-
-animation()
-test.screen.window.mainloop()
-
-############
diff --git a/dragExample.py b/dragExample.py
old mode 100644
new mode 100755
index 86f66d1..d25fc19
--- a/dragExample.py
+++ b/dragExample.py
@@ -1,29 +1,13 @@
-### Shark ###
+#!/usr/bin/python3
+# -*- coding: utf-8 -*-
+"""2 coordinates axes rotations with mouse."""
 
-import graphics.engine
+from graphics.engine import read_data_file, Engine3D
 
-points = []
-triangles = []
+vertices = read_data_file('coords/SharkV.txt', 'V')
+polygons = read_data_file('coords/SharkP.txt', 'P')
+test = Engine3D(vertices, polygons, scale=100, title='Shark')
 
-with open('coords/SharkV.txt', 'r') as f:
-    lines = f.readlines()
-    for line in lines:
-        coords = line[:-2].split(' ')
-        points.append([float(coords[0]), float(coords[1]), float(coords[2])])
-    f.close()
-
-with open('coords/SharkT.txt', 'r') as f:
-    lines = f.readlines()
-    for line in lines:
-        coords = line[:-2].split(' ')
-        newCoords = []
-        for coord in coords[1:4]:
-            newCoords.append(int(coord))
-        triangles.append(newCoords)
-    f.close()
-
-test = graphics.engine.Engine3D(points, triangles, scale=100, title='Shark')
-test.render()
-test.screen.window.mainloop()
-
-##############
+if __name__ == '__main__':
+    test.render()
+    test.screen.window.mainloop()
diff --git a/foldExample.py b/foldExample.py
new file mode 100755
index 0000000..1d5d0a9
--- /dev/null
+++ b/foldExample.py
@@ -0,0 +1,140 @@
+#!/usr/bin/python3
+# -*- coding: utf-8 -*-
+"""Folding management example.
+
+
+Origami pattern
+---------------
+
+Here we got an example of how graphical engine can use rotation around free
+axis.  We use those rotations on a rectangular paper sheet and fold it into
+origami card box.
+
+The origami pattern is flat modelised with final card box dimensions, so
+vertices coordinates are calculated accordly to few parameters.
+
+Folds are a bit complexe to describe:
+- Parameter is a list of step-folds;
+- Each step-fold is itself a list of line-folds moving together during the
+  folding step;
+- Each line-fold is a 4 tuple composed by:
+  - The angle value in degrees;
+  - 2 vertices indexes that defines the rotation axe (oriented);
+  - A list of vertices indexes that rotates around this .
+
+
+Commands
+--------
+
+A set of two new commmands are added to the keyboard binding:
+-<key N>: forward animation of the next fold
+-<key P>: backward animation of the previous fold
+
+
+Technical remarks
+-----------------
+
+- The current drawing engine uses a fast but simple ordering of faces on their
+z-middle-coordinate. Then faces are drawn from far to close, and close faces
+covers far ones. This way of rendering is quite good enougth to draw volumic
+models with single grid faces, but is doesn't render perfect for faces that are
+close and almost parallels like folded sheets of paper.  So, until the render
+engine is changed for a more complex and strict one, folded models may need to
+be turn around to be correctly drawn and understood.
+
+- Some patterns contains faces that are not triangles. Patterns would use a uniq
+color to show each rigid polygon (So 2 consecutive same color triangles do not
+fold in beetween in the final model - but they can fold a bit during folding for
+gaining light paper twist).
+
+- There is no management for polygons intersections during fold visualisation so
+there might be vertices that moves a little through faces. During real paper
+folding, paper polygons are flexibles so there is no problem.
+
+"""
+
+import graphics.engine
+
+# Flat pattern that folds into a parametric box.
+W = 1.3 # box width
+T = .5 # box thickness
+S = .01 # paper thickness causing a little shift on some faces (pre calculated in flat pattern).
+
+vertices = [
+    [-2.5*W-2*T+S, -.5*W, .5*T], [-1.5*W-2*T+S, -.5*W, .5*T], [-1.5*W-T, -.5*W, .5*T], # 0 1 2
+    [-.5*W-T, -.5*W, .5*T], [-.5*W, -.5*W, .5*T], [.5*W, -.5*W, .5*T+S/2], # 3 4 5
+    [.5*W+T-S, -.5*W, .5*T+S/2], [1.5*W+T-S, -.5*W, .5*T+S/2], [1.5*W+2*T-3*S, -.5*W, .5*T+S/2], # 6 7 8
+    [-2.5*W-2*T+S, .5*W, .5*T], [-1.5*W-2*T+S, .5*W, .5*T], [-1.5*W-T, .5*W, .5*T], # 9 10 11
+    [-.5*W-T, .5*W, .5*T], [-.5*W, .5*W, .5*T], [.5*W, .5*W, .5*T-S/2], # 12 13 14
+    [.5*W+T-S, .5*W, .5*T-S/2], [1.5*W+T-S, .5*W, .5*T-S/2], [1.5*W+2*T-3*S, .5*W, .5*T-S/2], # 15 16 17
+    [-2*W-2*T+S, 0, .5*T], [-1.5*W-1.5*T+S, 0, .5*T], [-1*W-T, 0, .5*T], # 18 19 20
+    [-.5*W-.5*T, 0, .5*T], [0, 0, .5*T], [.5*W+.5*T, 0, .5*T], # 21 22 23
+    [W+T-S, 0, .5*T], [1.5*W+1.5*T-S, 0, .5*T], # 24 25
+]
+
+polygons = [
+    [0, 1, 18, 'pink'], [0, 9, 18, 'pink'], [1, 10, 18, 'pink'], [9, 10, 18, 'pink'],
+    [1, 2, 19, 'red'], [1, 10, 19, 'red'], [2, 11, 19, 'red'], [10, 11, 19, 'red'],
+    [2, 3, 20, 'orange'], [2, 11, 20, 'orange'],
+    [3, 12, 20, 'gold'], [11, 12, 20, 'gold'],
+    [3, 4, 21, 'lime'], [3, 12, 21, 'lime'], [4, 13, 21, 'lime'], [12, 13, 21, 'lime'],
+    [4, 5, 22, 'green'], [4, 13, 22, 'green'], [5, 14, 22, 'green'], [13, 14, 22, 'green'],
+    [5, 6, 23, 'cyan'], [5, 14, 23, 'cyan'], [6, 15, 23, 'cyan'], [14, 15, 23, 'cyan'],
+    [6, 15, 24, 'royal blue'], [15, 16, 24, 'royal blue'],
+    [6, 7, 24, 'blue'], [7, 16, 24, 'blue'],
+    [7, 8, 25, 'purple'], [7, 16, 25, 'purple'], [8, 17, 25, 'purple'], [16, 17, 25, 'purple'],
+]
+
+PA = 15 # small angle to visualise paper marks in pre-fold
+
+folds = [
+    [ # pre mark for any final fold
+        (PA,  1, 10, [0, 9, 18]), # pink/red
+        (PA,  2, 11, [0, 1, 9, 10, 18, 19]), # red/orange
+        (PA, 11,  3, [0, 1, 2, 9, 10, 18, 19]), # orange/yellow
+        (PA, 12,  3, [0, 1, 2, 9, 10, 11, 18, 19, 20]), # yellow/lime
+        (PA, 13,  4, [0, 1, 2, 3, 9, 10, 11, 12, 18, 19, 20, 21]), # lime/green
+        (PA,  5, 14, [6, 7, 8, 15, 16, 17, 23, 24, 25]), # green/cyan
+        (PA,  6, 15, [7, 8, 16, 17, 24, 25]), # cyan/lightblue
+        (PA,  6, 16, [7, 8, 17, 25]), # lightblue/blue
+        (PA, 16,  7, [8, 17, 25]), # blue/purple
+    ], [ # first step-fold: outside pre 90° folds for bottom
+        (90-PA,  1, 10, [0, 9, 18]), # pink/red
+        (90-PA,  2, 11, [0, 1, 9, 10, 18, 19]), # red/orange
+        (90-PA, 16,  7, [8, 17, 25]), # blue/purple
+    ], [ # second step-fold: diagonals for triangle crossing in front part
+         # (not 180° to avoid face identity when draw)
+        (179-PA, 11,  3, [0, 1, 2, 9, 10, 18, 19]), # orange/yellow
+        (179-PA,  6, 16, [7, 8, 17, 25]), # lightblue/blue
+    ], [ # third step-fold: face bottom parts, left "outside" side
+        (30,  1,  9, [0]), # pink/pink
+        (10,  1, 10, [0, 9,  18]), # pink/red
+        (30, 11,  2, [0, 1, 9, 10, 18, 19]), # red/orange
+        (90-PA, 12,  3, [0, 1, 2, 9, 10, 11, 18, 19, 20]), # yellow/lime
+        (60-PA, 13,  4, [0, 1, 2, 3, 9, 10, 11, 12, 18, 19, 20, 21]), # lime/green
+    ], [ # fourth step-fold: face bottom parts, right "inside" side
+        (35,  5, 13, [6, 7, 8, 14, 15, 16, 17, 23, 24, 25]), # green/green
+        (45-PA,  5, 14, [6, 7, 8, 15, 16, 17, 23, 24, 25]), # green/cyan
+        (20,  6, 14, [7, 8, 15, 16, 17, 24, 25]), # cyan/cyan
+        (75-PA,  6, 15, [7, 8, 16, 17, 24, 25]), # cyan/lightblue
+        (60, 24,  7, [8, 16, 17, 25]), # blue/blue
+        (45, 16,  7, [8, 17, 25]), # blue/purple
+    ], [ # fifth step-fold: slide into bottom and complete box
+        (30,  9,  1, [0]), # pink/pink
+        (10, 10,  1, [0, 9, 18]), # pink/red
+        (30,  2, 11, [0, 1, 9, 10, 18, 19]), # red/orange
+        (30, 13,  4, [0, 1, 2, 3, 9, 10, 11, 12, 18, 19, 20, 21]), # lime/green
+        (35, 13,  5, [6, 7, 8, 14, 15, 16, 17, 23, 24, 25]), # green/green
+        (45,  5, 14, [6, 7, 8, 15, 16, 17, 23, 24, 25]), # green/cyan
+        (20, 14,  6, [7, 8, 15, 16, 17, 24, 25]), # cyan/cyan
+        (15,  6, 15, [7, 8, 16, 17, 24, 25]), # cyan/lightblue
+        (60,  7, 24, [8, 16, 17, 25]), # blue/blue
+        (45,  7, 16, [8, 17, 25]), # blue/purple
+    ]
+]
+
+test = graphics.engine.Engine3D(vertices, polygons, folds, title='Fold')
+
+if __name__ == '__main__':
+    test.render()
+    test.screen.window.mainloop()
diff --git a/galleonExample.py b/galleonExample.py
old mode 100644
new mode 100755
index c020e01..8071e5e
--- a/galleonExample.py
+++ b/galleonExample.py
@@ -1,28 +1,12 @@
-### Galleon ###
+#!/usr/bin/python3
+# -*- coding: utf-8 -*-
+"""Complex model example: Galleon"""
 
-import graphics.engine
+from graphics.engine import read_data_file, Engine3D
 
-points = []
-triangles = []
-
-with open('coords/GalleonV.txt', 'r') as f:
-    lines = f.readlines()
-    for line in lines:
-        coords = line[:-2].split(' ')
-        points.append([float(coords[0])/150, float(coords[1])/150, float(coords[2])/150])
-    f.close()
-
-with open('coords/GalleonT.txt', 'r') as f:
-    lines = f.readlines()
-    for line in lines:
-        coords = line[:-2].split(' ')
-        newCoords = []
-        for coord in coords[1:4]:
-            newCoords.append(int(coord))
-        triangles.append(newCoords)
-    f.close()
-
-test = graphics.engine.Engine3D(points, triangles, distance=100, title='Galleon')
+vertices = read_data_file('coords/GalleonV.txt', 'V', scale=1/150)
+polygons = read_data_file('coords/GalleonP.txt', 'P')
+test = Engine3D(vertices, polygons, distance=100, title='Galleon')
 
 def animation():
     test.clear()
@@ -30,7 +14,6 @@ def animation():
     test.render()
     test.screen.after(1, animation)
 
-animation()
-test.screen.window.mainloop()
-
-################
+if __name__ == '__main__':
+    animation()
+    test.screen.window.mainloop()
diff --git a/graphics/__pycache__/__init__.cpython-37.pyc b/graphics/__pycache__/__init__.cpython-37.pyc
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diff --git a/graphics/__pycache__/screen.cpython-37.pyc b/graphics/__pycache__/screen.cpython-37.pyc
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diff --git a/graphics/__pycache__/vertex.cpython-37.pyc b/graphics/__pycache__/vertex.cpython-37.pyc
deleted file mode 100644
index ddfb3d5..0000000
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diff --git a/graphics/__pycache__/vertex.cpython-38.pyc b/graphics/__pycache__/vertex.cpython-38.pyc
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diff --git a/graphics/engine.py b/graphics/engine.py
old mode 100644
new mode 100755
index 1725ce6..39f187d
--- a/graphics/engine.py
+++ b/graphics/engine.py
@@ -1,12 +1,75 @@
 import graphics.screen
-import graphics.face
-import graphics.vertex
+import graphics.structures
 import copy
 
+
+def read_data_file(filename, data_type, scale=1):
+    """Open a data file and creates a list of corresponding datas.
+
+    Data_type can be either 'V' for vertices coordinates (a line = 3 ints)
+    either 'P' for polygons (a line = an int for polygon size, n indexes of
+    vertices and an optional color name).
+
+    Scale is an optional zoom factor for vertices coordinates.
+    """
+    with open(filename, 'r') as f:
+        if data_type == 'V':
+            return [list(map(lambda c:float(c)*scale, l[:-1].strip().split())) for l in f.readlines()]
+        else: # data_type == 'P'
+            formated_lines = [l[:-1].strip().split() for l in f.readlines()]
+            return [list(map(int, fl[1:int(fl[0])+1])) + fl[int(fl[0])+1:] for fl in formated_lines]
+
+
 class Engine3D:
-    def __resetDrag(self, event):
+    # number of pictures in fold animations
+    anim_steps = 20
+    # colors for show vectors in grabbing
+    axis_colors = ['red', 'green', 'blue']
+
+    def __init__(self, vertices, polygons, folds=[], width=1000, height=700, distance=6, scale=100, title='3D', background='white'):
+        # vertices
+        self.vertices = [graphics.structures.Vertex(v) for v in vertices]
+        # faces
+        self.polygons = [graphics.structures.Polygon(*p) for p in polygons]
+        # folds
+        self.folds = folds
+
+        # initialize display
+        self.screen = graphics.screen.Screen(width, height, title, background)
+
+        # viewing
+        self.distance = distance
+        self.scale = scale
+        self.screen.window.bind('<ButtonRelease-4>', self.__zoom_in)
+        self.screen.window.bind('<ButtonRelease-5>', self.__zoom_out)
+        self.screen.window.bind('<Up>', self.__camera_up)
+        self.screen.window.bind('<Down>', self.__camera_down)
+        self.screen.window.bind('<Left>', self.__camera_left)
+        self.screen.window.bind('<Right>', self.__camera_right)
+
+        # folding animation
+        self.fold_index = 0
+        self.screen.window.bind('n', self.__next_fold)
+        self.screen.window.bind('p', self.__prev_fold)
+
+        # grabbing
+        self.__reset_drag()
+        self.screen.window.bind('<B1-Motion>', self.__drag)
+        self.screen.window.bind('<ButtonRelease-1>', self.__reset_drag)
+
+        # model edition
+        self.__selected = None
+        self.screen.window.bind('<ButtonPress-3>', self.__select)
+        self.screen.window.bind('<ButtonRelease-3>', self.__deselect)
+        self.screen.window.bind('x', self.__select_x)
+        self.screen.window.bind('y', self.__select_y)
+        self.screen.window.bind('z', self.__select_z)
+        self.screen.window.bind('+', self.__move_down)
+        self.screen.window.bind('-', self.__move_up)
+
+    def __reset_drag(self, event=None):
         self.__prev = []
-    
+
     def __drag(self, event):
         if self.__prev:
             self.rotate('y', (event.x - self.__prev[0]) / 20)
@@ -15,164 +78,135 @@ def __drag(self, event):
             self.render()
         self.__prev = [event.x, event.y]
 
+    def __build_axis(self, selection, direction, orientation):
+        res = copy.deepcopy(selection)
+        setattr(res, direction, getattr(res, direction) + 40 * orientation / self.scale)
+        res.flatten(self.scale, self.distance)
+        return (res.get_flat()[0] + self.screen.zeros[0], res.get_flat()[1] + self.screen.zeros[1])
+
     def __select(self, event):
         zeros = self.screen.zeros
-        event = (event.x - zeros[0], event.y - zeros[1])
-            
-        possibilities = []
-        for a in range(-6, 5):
-            for b in range(-6, 5):
-                possibilities.append((event[0] + a, event[1] + b))
-
-        found = [e for e in possibilities if e in self.flattened]
-        if found != []:
+        ex, ey = event.x - zeros[0], event.y - zeros[1]
+        exm, exp, eym, eyp = ex - 6, ex + 5, ey - 6, ey + 5
+        possible_vertices = [i for i,v in enumerate(self.vertices)
+                               if exm < v.flat_x < exp and eym < v.flat_y < eyp]
+        if possible_vertices != []:
             self.__moveaxis = None
-            self.__selected = self.flattened.index(found[0])
-
-            i = self.points[self.__selected]
-            self.__axis = [[copy.deepcopy(i) for a in range(2)] for b in range(3)]
-            
-            self.__axis[0][0].x -= 40 / self.scale
-            self.__axis[0][1].x += 40 / self.scale
-            self.__axis[1][0].y -= 40 / self.scale
-            self.__axis[1][1].y += 40 / self.scale
-            self.__axis[2][0].z -= 40 / self.scale
-            self.__axis[2][1].z += 40 / self.scale
-            
-            self.__axis = [[point.flatten(self.scale, self.distance) for point in i] for i in self.__axis]
-            self.__axis = [[[i[0] + zeros[0], i[1] + zeros[1]] for i in j] for j in self.__axis]
-            self.__axis = [self.screen.createLine(self.__axis[0], 'red'), self.screen.createLine(self.__axis[1], 'green'), self.screen.createLine(self.__axis[2], 'blue')]
-
-    def __selectx(self, event):
+            self.__selected = self.vertices[possible_vertices[0]]
+            axis = [[self.__build_axis(self.__selected, d, o) for o in [-1,1]] for d in 'xyz']
+            self.__axis = [self.screen.create_arrow(a, self.axis_colors[i]) for i,a in enumerate(axis)]
+
+    def __select_x(self, event):
         self.__moveaxis = 'x'
 
-    def __selecty(self, event):
+    def __select_y(self, event):
         self.__moveaxis = 'y'
 
-    def __selectz(self, event):
+    def __select_z(self, event):
         self.__moveaxis = 'z'
 
-    def __moveup(self, event):
+    def __move_up(self, event):
         if self.__selected != None and self.__moveaxis != None:
-            self.points[self.__selected].move(self.__moveaxis, 0.1)
+            self.__selected.move(self.__moveaxis, 0.1)
             self.clear()
             self.render()
 
-    def __movedown(self, event):
+    def __move_down(self, event):
         if self.__selected != None and self.__moveaxis != None:
-            self.points[self.__selected].move(self.__moveaxis, -0.1)
+            self.__selected.move(self.__moveaxis, -0.1)
             self.clear()
             self.render()
 
-    def __zoomin(self, event):
+    def __deselect(self, event):
+        if self.__selected != None:
+            self.__selected = None
+            for line in self.__axis:
+                self.screen.delete(line)
+            self.__axis = []
+
+    def __zoom_in(self, event):
         self.scale += 2.5
         self.clear()
         self.render()
 
-    def __zoomout(self, event):
+    def __zoom_out(self, event):
         self.scale -= 2.5
         self.clear()
         self.render()
 
-    def __deselect(self, event):
-        if self.__selected != None:
-            self.__selected = None
-            self.__axis = [self.screen.delete(line) for line in self.__axis]
-            self.__moveaxis = None
-
-    def __cameraleft(self, event):
+    def __camera_left(self, event):
         self.screen.zeros[0] -= 5
         self.clear()
         self.render()
 
-    def __cameraright(self, event):
+    def __camera_right(self, event):
         self.screen.zeros[0] += 5
         self.clear()
         self.render()
 
-    def __cameraup(self, event):
+    def __camera_up(self, event):
         self.screen.zeros[1] -= 5
         self.clear()
         self.render()
 
-    def __cameradown(self, event):
+    def __camera_down(self, event):
         self.screen.zeros[1] += 5
         self.clear()
         self.render()
-        
-    def writePoints(self, points):
-        self.points = []
-        for point in points:
-            self.points.append(graphics.vertex.Vertex(point))
-            
-    def writeTriangles(self, triangles):
-        self.triangles = []
-        for triangle in triangles:
-            if len(triangle) != 4:
-                triangle.append('gray')
-            self.triangles.append(graphics.face.Face(triangle))
-            
-    def __init__(self, points, triangles, width=1000, height=700, distance=6, scale=100, title='3D', background='white'):
-        #object parameters
-        self.distance = distance
-        self.scale = scale
 
-        #initialize display
-        self.screen = graphics.screen.Screen(width, height, title, background)
-        self.screen.window.bind('<B1-Motion>', self.__drag)
-        self.__prev = []
-        self.screen.window.bind('<ButtonRelease-1>', self.__resetDrag)
+    def __next_fold(self, event):
+        if self.fold_index < len(self.folds):
+            for i in range(self.anim_steps):
+                self.screen.after(int(1000/self.anim_steps), self.__fold_animate(self.folds[self.fold_index]))
+            self.fold_index += 1
+
+    def __prev_fold(self, event):
+        if self.fold_index > 0:
+            for i in range(self.anim_steps):
+                self.screen.after(int(1000/self.anim_steps), self.__fold_animate(self.folds[self.fold_index-1],False))
+            self.fold_index -= 1
+
+    def __fold_animate(self, folds, do=True):
+        for subfolds in folds:
+            angle, axe1, axe2, vertices = subfolds
+            if do == True:
+                angle = angle / self.anim_steps
+            else:
+                angle = -angle / self.anim_steps
+            self.part_free_rotate(angle, axe1, axe2, vertices)
+        self.clear()
+        self.render()
+        self.screen.window.update_idletasks()
 
-        self.screen.window.bind('<Up>', self.__zoomin)
-        self.screen.window.bind('<Down>', self.__zoomout)
-        self.screen.window.bind('w', self.__cameraup)
-        self.screen.window.bind('s', self.__cameradown)
-        self.screen.window.bind('a', self.__cameraleft)
-        self.screen.window.bind('d', self.__cameraright)
+    def rotate(self, axis, angle):
+        # rotate model around axis
+        for point in self.vertices:
+            point.rotate(axis, angle)
 
-        # this is for editing the model
-        self.__selected = None
-        self.__axis = []
-        self.__moveaxis = None
-        self.screen.window.bind('<ButtonPress-3>', self.__select)
-        self.screen.window.bind('<ButtonRelease-3>', self.__deselect)
-        self.screen.window.bind('x', self.__selectx)
-        self.screen.window.bind('y', self.__selecty)
-        self.screen.window.bind('z', self.__selectz)
-        self.screen.window.bind('<Left>', self.__movedown)
-        self.screen.window.bind('<Right>', self.__moveup)
-        
-        #store coordinates
-        self.writePoints(points)
-        self.flattened = []
-
-        #store faces
-        self.writeTriangles(triangles)
+    def part_free_rotate(self, angle, A, B, vertices):
+        # rotate part of model around free vector (from self.vertices[A] to self.vertices[B])
+        for point in [self.vertices[index] for index in vertices]:
+            point.free_rotate(angle, self.vertices[A], self.vertices[B])
+
+    def free_rotate(self, angle, A, B):
+        # rotate model around free vector (from self.vertices[A] to self.vertices[B])
+        for point in self.vertices:
+            point.free_rotate(angle, self.vertices[A], self.vertices[B])
 
     def clear(self):
-        #clear display
+        # clear display
         self.screen.clear()
 
-    def rotate(self, axis, angle):
-        #rotate model around axis
-        for point in self.points:
-            point.rotate(axis, angle)
-
     def render(self):
-        #calculate flattened coordinates (x, y)
-        self.flattened = []
-        for point in self.points:
-            self.flattened.append(point.flatten(self.scale, self.distance))
-
-        #get coordinates to draw triangles
-        triangles = []
-        for triangle in self.triangles:
-            avgZ = -(self.points[triangle.a].z + self.points[triangle.b].z + self.points[triangle.c].z) / 3
-            triangles.append((self.flattened[triangle.a], self.flattened[triangle.b], self.flattened[triangle.c], triangle.color, avgZ))
-
-        #sort triangles from furthest back to closest
-        triangles = sorted(triangles,key=lambda x: x[4])
-
-        #draw triangles
-        for triangle in triangles:
-            self.screen.createTriangle(triangle[0:3], triangle[3])
+        # flatten vertices into screen positions
+        for vert in self.vertices:
+            vert.flatten(self.scale, self.distance)
+
+        # calculate polygons average depth (z)
+        for poly in self.polygons:
+            poly.depth = sum([self.vertices[v_i].z for v_i in poly.vertices])
+
+        # draw flattent polygons from furthest to closest
+        for poly in reversed(sorted(self.polygons, key=lambda x: x.depth)):
+            self.screen.create_polygon([self.vertices[v].get_flat() for v in poly.vertices], poly.color)
+
diff --git a/graphics/face.py b/graphics/face.py
deleted file mode 100644
index 80fa5f3..0000000
--- a/graphics/face.py
+++ /dev/null
@@ -1,8 +0,0 @@
-class Face:
-    def __init__(self, vertices):
-        #store point indexes
-        (a, b, c, color) = vertices
-        self.a = a
-        self.b = b
-        self.c = c
-        self.color = color
diff --git a/graphics/screen.py b/graphics/screen.py
index f294120..52f3a71 100644
--- a/graphics/screen.py
+++ b/graphics/screen.py
@@ -1,4 +1,5 @@
 import tkinter
+import itertools
 
 class Screen:
     def __init__(self, width, height, title, background):
@@ -10,15 +11,14 @@ def __init__(self, width, height, title, background):
         self.window.title(title)
         self.image = tkinter.Canvas(self.window, width=width, height=height, bg=background)
         self.image.pack()
-    
-    def createTriangle(self, points, color):
-        a, b, c = points[0], points[1], points[2]
-        #create coordinates starting in center of screen
-        coords = [a[0] + self.zeros[0], a[1] + self.zeros[1], b[0] + self.zeros[0], b[1] + self.zeros[1], c[0] + self.zeros[0], c[1] + self.zeros[1]]
-        #draw triangle on screen
+
+    def create_polygon(self, vertices, color):
+        # create coordinates starting in center of screen
+        coords = list(itertools.chain(*[[v0 + self.zeros[0], v1 + self.zeros[1]] for v0,v1 in vertices]))
+        # draw triangle on screen
         self.image.create_polygon(coords, fill=color, outline="black")
 
-    def createLine(self, points, color):
+    def create_arrow(self, points, color):
         a, b = points[0], points[1]
         return self.image.create_line(a[0], a[1], b[0], b[1], fill=color, arrow=tkinter.BOTH)
 
@@ -28,7 +28,6 @@ def clear(self):
 
     def delete(self, item):
         self.image.delete(item)
-        return None
 
     def after(self, time, function):
         #call tk.Tk's after() method
diff --git a/graphics/structures.py b/graphics/structures.py
new file mode 100644
index 0000000..2660d14
--- /dev/null
+++ b/graphics/structures.py
@@ -0,0 +1,92 @@
+import math
+
+
+class Polygon:
+    def __init__(self, *args):
+        #store point indexes
+        if isinstance(args[-1], str):
+            self.vertices = args[:-1]
+            self.color = args[-1]
+        else:
+            self.vertices = args
+            self.color = "grey"
+
+
+class Vertex:
+    def __init__(self, point):
+        #store x, y, z coordinates
+        (x,y,z) = point
+        self.x = x
+        self.y = y
+        self.z = z
+
+    def flatten(self, scale, distance):
+        #calculate 2D coordinates from 3D point
+        self.flat_x = int(((self.x * distance) / (self.z + distance)) * scale)
+        self.flat_y = int(((self.y * distance) / (self.z + distance)) * scale)
+
+    def get_flat(self):
+        return (self.flat_x, self.flat_y)
+
+    def rotate(self, axis, angle):
+        #rotate point around axis
+        angle = angle / 450 * 180 / math.pi
+        #sqrt2 = math.sqrt(2)
+        if axis == 'z':
+            #rotate aroud Z axis
+            newX = self.x * math.cos(angle) - self.y * math.sin(angle)
+            newY = self.y * math.cos(angle) + self.x * math.sin(angle)
+            newZ = self.z
+        elif axis == 'x':
+            #rotate around X axis
+            newY = self.y * math.cos(angle) - self.z * math.sin(angle)
+            newZ = self.z * math.cos(angle) + self.y * math.sin(angle)
+            newX = self.x
+        elif axis == 'y':
+            #rotate around Y axis
+            newX = self.x * math.cos(angle) - self.z * math.sin(angle)
+            newZ = self.z * math.cos(angle) + self.x * math.sin(angle)
+            newY = self.y
+        else:
+            raise ValueError('invalid rotation axis')
+        self.x = newX
+        self.y = newY
+        self.z = newZ
+
+    def move(self, axis, value):
+        if axis == 'x':
+            self.x += value
+        elif axis == 'y':
+            self.y += value
+        elif axis == 'z':
+            self.z += value
+        else:
+            raise ValueError('Invalid movement axis')
+
+    def free_rotate(self, phi, A, B):
+        """Compute new coordinates for self as image of itself by the rotation R
+        of phi degrees around the AB vector."""
+        # Define conjugate and * for Quaternions (4-tuples)
+        class Quaternion(tuple):
+            def conj(self):
+                return self[0], *[-self[i] for i in range(1,4)]
+            def __mul__(self, q2):
+                w1, x1, y1, z1 = self
+                w2, x2, y2, z2 = q2
+                w = w1 * w2 - x1 * x2 - y1 * y2 - z1 * z2
+                x = w1 * x2 + x1 * w2 + y1 * z2 - z1 * y2
+                y = w1 * y2 + y1 * w2 + z1 * x2 - x1 * z2
+                z = w1 * z2 + z1 * w2 + x1 * y2 - y1 * x2
+                return w, x, y, z
+        # Compute "vector to rotate" quaternion using vector Aself.
+        p = Quaternion((0, self.x-A.x, self.y-A.y, self.z-A.z))
+        # Compute "rotation" quaternion using vector of AB.
+        ABx, ABy, ABz = B.x-A.x, B.y-A.y, B.z-A.z
+        nAB = math.sqrt(ABx**2 + ABy**2 + ABz**2)
+        half_phi_rad = phi / 360 * math.pi
+        S = math.sin(half_phi_rad)
+        r = Quaternion((math.cos(half_phi_rad), S*ABx/nAB, S*ABy/nAB, S*ABz/nAB))
+        # Calculate "image" quaternion using p and r conjugation (q = r⋅p⋅r^-1).
+        qw, qx, qy, qz = Quaternion(r * p) * r.conj()
+        # Get Q coordinates.
+        self.x, self.y, self.z = qx+A.x, qy+A.y, qz+A.z
diff --git a/graphics/vertex.py b/graphics/vertex.py
deleted file mode 100644
index 66dc6be..0000000
--- a/graphics/vertex.py
+++ /dev/null
@@ -1,51 +0,0 @@
-import math
-
-class Vertex:
-    def __init__(self, point):
-        #store x, y, z coordinates
-        (x,y,z) = point
-        self.x = x
-        self.y = y
-        self.z = z
-
-    def flatten(self, scale, distance):
-        #calculate 2D coordinates from 3D point
-        projectedY = int(((self.y * distance) / (self.z + distance)) * scale)
-        projectedX = int(((self.x * distance) / (self.z + distance)) * scale)
-        return (projectedX, projectedY)
-
-    def rotate(self, axis, angle):
-        #rotate point around axis
-        angle = angle / 450 * 180 / math.pi
-        sqrt2 = math.sqrt(2)
-        if axis == 'z':
-            #rotate aroud Z axis
-            newX = self.x * math.cos(angle) - self.y * math.sin(angle)
-            newY = self.y * math.cos(angle) + self.x * math.sin(angle)
-            newZ = self.z
-        elif axis == 'x':
-            #rotate around X axis
-            newY = self.y * math.cos(angle) - self.z * math.sin(angle)
-            newZ = self.z * math.cos(angle) + self.y * math.sin(angle)
-            newX = self.x
-        elif axis == 'y':
-            #rotate around Y axis
-            newX = self.x * math.cos(angle) - self.z * math.sin(angle)
-            newZ = self.z * math.cos(angle) + self.x * math.sin(angle)
-            newY = self.y
-        else:
-            raise ValueError('invalid rotation axis')
-        self.x = newX
-        self.y = newY
-        self.z = newZ
-
-    def move(self, axis, value):
-        if axis == 'x':
-            self.x += value
-        elif axis == 'y':
-            self.y += value
-        elif axis == 'z':
-            self.z += value
-        else:
-            raise ValueError('Invalid movement axis')
-
diff --git a/pyramidExample.py b/pyramidExample.py
new file mode 100755
index 0000000..dd7f790
--- /dev/null
+++ b/pyramidExample.py
@@ -0,0 +1,19 @@
+#!/usr/bin/python3
+# -*- coding: utf-8 -*-
+"""Animated pyramid example"""
+
+from graphics.engine import Engine3D
+
+vertices = [[0,0,0],[0,-1,0],[-1,1,-1],[-1,1,1],[1,1,1],[1,1,-1]]
+polygons = [[2,3,4,5],[1,2,3],[1,3,4],[1,4,5],[1,2,5]]
+test = Engine3D(vertices, polygons, title='Cube')
+
+def animation():
+    test.clear()
+    test.free_rotate(.75, 0, 1) # angle in degree, axe defined by 2 vertices
+    test.render()
+    test.screen.after(10, animation)
+
+if __name__ == '__main__':
+    animation()
+    test.screen.window.mainloop()
diff --git a/sharkExample.py b/sharkExample.py
old mode 100644
new mode 100755
index 895ceef..0d5bb3c
--- a/sharkExample.py
+++ b/sharkExample.py
@@ -1,28 +1,12 @@
-### Shark ###
+#!/usr/bin/python3
+# -*- coding: utf-8 -*-
+"""Complex model example: Shark"""
 
-import graphics.engine
+from graphics.engine import read_data_file, Engine3D
 
-points = []
-triangles = []
-
-with open('coords/SharkV.txt', 'r') as f:
-    lines = f.readlines()
-    for line in lines:
-        coords = line[:-2].split(' ')
-        points.append([float(coords[0]), float(coords[1]), float(coords[2])])
-    f.close()
-
-with open('coords/SharkT.txt', 'r') as f:
-    lines = f.readlines()
-    for line in lines:
-        coords = line[:-2].split(' ')
-        newCoords = []
-        for coord in coords[1:4]:
-            newCoords.append(int(coord))
-        triangles.append(newCoords)
-    f.close()
-
-test = graphics.engine.Engine3D(points, triangles, scale=100, title='Shark')
+vertices = read_data_file('coords/SharkV.txt', 'V')
+polygons = read_data_file('coords/SharkP.txt', 'P')
+test = Engine3D(vertices, polygons, scale=100, title='Shark')
 
 def animation():
     test.clear()
@@ -30,7 +14,6 @@ def animation():
     test.render()
     test.screen.after(1, animation)
 
-animation()
-test.screen.window.mainloop()
-
-##############
+if __name__ == '__main__':
+    animation()
+    test.screen.window.mainloop()