//Snake S = new Snake(50);
Snake S = new Snake(500);

class Snake { 
  int nmax=1000;
  int n=0;
  pt S[] = new pt[nmax];
  float L[] = new float [nmax], R[] = new float [nmax], W[] = new float [nmax], B[] = new float [nmax];
  Snake() {};
  Snake(int pn) {n=pn; println("snake of "+n);};
  void declare() {for(int i=0; i<nmax; i++) {S[i]=new pt(0,0);};}
  void resert() {n=0; }
  void straighten() {body(0.02,0.0,2,0);}
  void add(pt P, float pW, float pB, float pL, float pR) {S[n].setFromPt(P); W[n]=pW; B[n]=pB; R[n]=pR; L[n]=pL; n++;}
  void add(float x, float y, float pW, float pB, float pL, float pR) {S[n].setFromValues(x,y); W[n]=pW; B[n]=pB; R[n]=pR; L[n]=pL; n++;}
  void body(float r, float w, float p, float o) {for(int i=0; i<n; i++) {S[i].setFromValues(width/10+width*0.80*i/n,height/2+taper(w*height*sin(TWO_PI*(i+o)*p/n),i,n)); W[i]=r*height;};}
  void bulge(float b, float p, float o) {for(int i=0; i<n; i++) B[i]=max(0,taper(b*height*sin(TWO_PI*(i+o)*p/n),i,n));}
  void wrinklesL(float w, int p, float o) {for(int i=0; i<n; i++) {L[i]=taper(w*height,i,n); if (int((i+o))%p!=0) L[i]=0;};}
  void wrinklesR(float w, int p, float o) {for(int i=0; i<n; i++) {R[i]=taper(w*height,i,n); if (int((i+o))%p!=0) R[i]=0;};}
  void showBody() {for(int i=0; i<n; i++) S[i].show(W[i]);};
  void showWrinklesL() {for(int i=1; i<n-1; i++) offset(S[i-1],S[i],S[i+1],W[i-1]+B[i-1],W[i]+B[i],W[i+1]+B[i+1],1).show(L[i]);};
  void showWrinklesR() {for(int i=1; i<n-1; i++) offset(S[i-1],S[i],S[i+1],W[i-1]+B[i-1],W[i]+B[i],W[i+1]+B[i+1],-1).show(R[i]);};
  void showBulge() {for(int i=0; i<n; i++) S[i].show(B[i]+W[i]);};
  }

float taper (float v, int i, int n) {if (i<n/4) return (1-sq(cos(PI*i/n*2)))*v; else if (i>3*n/4) return (1-sq(cos(PI*(i-n/2)/n*2)))*v; else return v; }

pt offset(pt A, pt B, pt C, float a, float b, float c, float s) {
  float x,y, dr;                // displacements and radius derivative
     vec V=A.vecTo(C); float nn= V.norm(); V.unit(); vec N=V.left();
     dr=(c-a)/nn;     x=-dr*b;     y=sqrt(sq(b)-sq(x)); 
     pt H=B.makeCopy();  H.addScaledVec(x,V); H.addScaledVec(s*y,N);
     return H;
   }