diff --git a/22.jpg b/22.jpg
new file mode 100644
index 0000000..3e0b520
Binary files /dev/null and b/22.jpg differ
diff --git a/3.jpg b/3.jpg
new file mode 100644
index 0000000..0b0545c
Binary files /dev/null and b/3.jpg differ
diff --git a/4.jpg b/4.jpg
new file mode 100644
index 0000000..9bb2c0b
Binary files /dev/null and b/4.jpg differ
diff --git a/index.html b/index.html
index 6cde78c..37b8809 100644
--- a/index.html
+++ b/index.html
@@ -22,7 +22,7 @@
 <body bgcolor=white text=black link=black alink=blue vlink=blue>
 <center>
    <!!--- SUPER SAMPLING THE W/H PARAMS FOR CANVAS ARE RENDER SIZE, IN THE CSS IS ACTUAL(DISPLAY) SIZE.--->
-<canvas id='canvas1' style="width: 600px; height:600px;" width=1200 height=1200></canvas>
+<canvas id='canvas1' style="overflow: auto; width: 600px; height:600px;" width=1200 height=1200></canvas>
 </center>
 </body>
 
@@ -40,7 +40,7 @@
 
 
 <!!-------- FRAGMENT SHADER: THIS IS WHERE YOU WILL DO YOUR WORK -------->
-<!!-------- FRAGMENT SHADER: MOVED TO ./shader.frag LOADED IN lib2.js -------->
+<!!-------- FRAGMENT SHADER: MOVED TO ./shader.frag!! LOADED IN lib2.js -------->
 <!--script src="shader.frag" id='my_fragment_shader' type='x-shader/x-fragment'> </script>
 
 
@@ -65,24 +65,24 @@ Solar RTX
    <li>Ctrl+Alt/Option+N: Reset ViewPoint.</li>
    <li>Ctrl+Alt/Option+P: Toggle Pause/Resume.</li>
    <li style="color:red;">Please unfocus the Editing area (click somewhere else on the page) to use hotkeys.</li>
-   <li>Click on canvas (WITHOUT key modifiers): Toggle Pause/Resume.</li>
-   <li>SHIFT+Alt/Option+MOUSE DRAG/WHEEL ZOOM: Changing Viewing point.</li>
-
+   <li>Double Click on canvas (WITHOUT key modifiers): Toggle Pause/Resume.</li>
+   <li>MOUSE DRAG, SCROLL/WHEEL ZOOM: Changing Viewing point.</li>
+   <li>Use Chromium based browser for better performance.</li>
 </ul>
 <i style="font-size:25px;">How it works:</i>
 <ul>
-   <li>First, I started with what I've already done in homework 1. Which already included complete Phong shading with 
+   <li>First, I started with what I've already done in <a href="https://billsun.dev/graphics/hw1">homework 1</a>. Which already included complete Phong shading with 
       Specular light and much more (spherical texture mapping, simple interactions, improved UI/shader editor).
    </li>
    <li> I then merged the code from hw2 and added texture to each sphere.</li>
-   <li> I modified the ray tracing algorithm so that when hitting an object, instead of returning color calculated from 
+   <li> I modified the ray tracing algorithm so that when hitting an object, instead of just returning color calculated from 
       Phong model:<br>
       <ul>
          <li>It recursively bounces and/or refract(NOT IMPLEMENTED YET) itself spawning new rays.</li>
          <li>The color of this pixel equals to Ambient + Diffuse + ks*color[Reflected] + kt*color[Refracted]. 
             (<a href="https://www.cs.drexel.edu/~david/Classes/Papers/p343-whitted.pdf">Turner Whitted Model</a>)</li>
-         <li>The tracing will stop when a ray was reflected/refracted n_ref times. </li> 
-         <li>The color of the final light is computed via specular component from the Phong model.</li>
+         <li>The tracing will stop when a ray was not hitting any object or was reflected/refracted n_ref times. </li> 
+         <li>The color/intensity of the final lights are computed via specular component from the Phong model.</li>
          <li>You may increase n_ref for more iterations, but please proceed with caution, because it may halt the computer.  
          </li>
       </ul>
@@ -91,7 +91,7 @@ Solar RTX
       or holding shift and alt while scrolling on canvas to change focal length.
       This is implemented by applying a transformation matrix to the viewpoint and projection surface.
    </li>   
-   <li>Finally, I used super sampling via doubling the render dimensions of the canvas to reduce aliasing.</li>
+   <li>Finally, I used super sampling via doubling the render dimensions of the canvas to reduce aliasing. SEE comments on index.html</li>
    <li>Repo on <a href="https://github.com/sunyinqi0508/graphics_hw1">Github</a>.</li>
    </li>
  </ul>
@@ -135,13 +135,26 @@ document.body.innerHTML = [''
    ,'<table cellspacing=0>'
    ,'<tr>'
    ,'<td valign=top>'
-   ,'<div id="ace" style="width:800px;height:1780px;"></div>'
+   ,'<div id="ace" style="width:800px;height:2200px;"></div>'
    ,'</td><td valign=top>' + document.body.innerHTML
+   ,'<input type="number" id="ins" style="margin-left:3px;font-size:24px;width:100px;height:45px" value="4">'
+   ,'<button id="bns" style="margin-left:5px;font-size:24px;width:150px;height:45px">Set Spheres</button>'
    ,'<div style=\'font-size:25px\'>' + my_instructions.innerHTML + '</div>' + '</td>'
    ,'</tr></table>'
    ,'</TR></TABLE>'
    ].join('');
-
+bns.onclick=function(e){
+   if(ins.value>0 &&ins.value<=ns &&cns!=ins.value)
+   {   
+      cns = ins.value;
+      fragmentShaderDefs = '\n const int cns = ' + cns + ';';
+      if(typeof canvas1.setShaders === "function")
+         {
+            canvas1.setShaders(vs, editor.getSession().getValue());
+            setUniform('1i', 'flags', flags);
+         }
+   }
+}
 // SET UP THE EDITABLE TEXT AREA ON THE LEFT SIDE.
 ace.require("ace/ext/language_tools");
 var editor = ace.edit("ace", {
@@ -163,9 +176,11 @@ editor.setAutoScrollEditorIntoView(true);
 delete editor.KeyBinding;
 let lastTime = Date.now();
 let animating = true;
-let ctrl = false, alt = false, shift = false, fpson = true, moving = false;
+let ctrl = false, alt = false, shift = false, fpson = true, moving = false, over = false;
 let mousedx = 0, mousedy = 0, mousedz = 0;
+let cx = 1, cy = 1, sx = 0, sy = 0;
 let mouselastX, mouselastY;
+let lastClick = undefined;
 let pause_resume = function(){
    if(animating)
          lastTime = Date.now();
@@ -174,30 +189,46 @@ let pause_resume = function(){
       animating = !animating;
 };
 canvas1.addEventListener('click',function(ev){
-   if(!(shift && alt))
+   if(!(shift && alt) && lastClick&& Date.now()-lastClick<400)
       pause_resume();
+   lastClick = Date.now();
    //moving = false;
 });
+canvas1.addEventListener('mouseover', function(e){
+   over = true;
+   const mask = 0x8;
+   flags |= mask;
+   setUniform('1i', 'flags', flags);
+});
 canvas1.addEventListener('mousedown', function(e){
-   if(shift && alt){
       moving = true
       mouselastX = mouselastY =  undefined;
-   }
-   else
-      moving = false;
 });
 canvas1.addEventListener('mousemove', function(e){
-   if(shift && alt && moving){
-      if(!(mouselastX==undefined || mouselastY == undefined)){
-         mousedx += (mouselastX - e.offsetX)/60;
-         mousedy += (mouselastY - e.offsetY)/60;
-         setUniform('4f', 'rot', Math.cos(mousedx), Math.sin(mousedx), Math.cos(mousedy), Math.sin(mousedy));
+      if(!(mouselastX==undefined || mouselastY == undefined)&&moving){
+         mousedx -= (mouselastX - e.offsetX)/60;
+         mousedy -= (mouselastY - e.offsetY)/60;
+         cx = Math.cos(mousedx);
+         sx = Math.sin(mousedx);
+         cy = Math.cos(mousedy);
+         sy = Math.sin(mousedy);
+         setUniform('4f', 'rot', cx, sx, cy, sy);
+         const mask = 0x4;
+         flags |= mask;
+         setUniform('1i', 'flags', flags);
       }
+      // if(over){
+      //    let x=e.offsetX/300-1;
+      //    let y=e.offsetY/300-1;
+      //    let z=-1-3-mousedz;
+      //    let tx = cx*x+sy*sx*y+sx*cy*z;
+      //    let ty = cy*y-sy*z;
+      //    let tz = -sx*x+cx*sy*y+cx*cy*z;
+      //    let len = Math.sqrt(tx*tx + ty*ty+tz*tz);
+      //    setUniform('3f', 'fDir', tx/len, ty/len, tz/len);
+      // }
       mouselastX = e.offsetX;
       mouselastY = e.offsetY;
-   }
-   else
-      moving = false;
 });
 canvas1.addEventListener('mouseup', function(e){
    // if(ctrl && alt && moving){
@@ -207,14 +238,18 @@ canvas1.addEventListener('mouseup', function(e){
 canvas1.addEventListener('mouseout', function(e){
    // if(ctrl && alt && moving){
    // }
+   const mask = 0x8;
+   flags &= !mask;
+   setUniform('1i', 'flags', flags);
+   over = false;
    moving = false;
 });
 canvas1.addEventListener('wheel', function(e){
-   if(shift && alt){
       mousedz += e.wheelDelta/600;
       setUniform('1f', 'dFL', mousedz);
-   }
+      e.stopImmediatePropagation();
 });
+canvas1.scroll(function(e) {e.stopPropagation();});
 rtx.style.cursor="pointer";
 let rtswitch = function(){
    const mask = 0x2;
@@ -223,7 +258,7 @@ let rtswitch = function(){
       rtx.src='./RTXoff.svg';
    else
       rtx.src='./RTXon.svg';
-   flags = flags&!mask | (rtstatus?mask:0);
+   flags = (flags&(!mask)) | (rtstatus?mask:0);
    setUniform('1i', 'flags', flags);
 }
 rtx.addEventListener('click', rtswitch);
@@ -267,7 +302,12 @@ document.addEventListener('keydown',(e)=>{
       flags = 0;
       moving = false;
       mousedx = mousedy = mousedz = 0;
-      setUniform('4f', 'rot', Math.cos(mousedx), Math.sin(mousedx), Math.cos(mousedy), Math.sin(mousedy));
+      cx = Math.cos(mousedx);
+      sx = Math.sin(mousedx);
+      cy = Math.cos(mousedy);
+      sy = Math.sin(mousedy);
+      rtx.src='./RTXon.svg';
+      setUniform('4f', 'rot', cx, sx, cy, sy);
       setUniform('1f', 'dFL', mousedz);
       setUniform('1i', 'flags', flags);
    }
diff --git a/lib2.js b/lib2.js
index 196053f..2dde401 100644
--- a/lib2.js
+++ b/lib2.js
@@ -15,8 +15,10 @@ let fragmentShaderHeader = [''                      // WHATEVER CODE WE WANT TO
    , '  r+=sin(6.3*dot(P,fract(D)-.5))*pow(max(0.,1.-2.*dot(P,P)),4.);'
    , '} return .5 * sin(r); }'
 ].join('\n');
-
-let nfsh = fragmentShaderHeader.split('\n').length; // NUMBER OF LINES OF CODE IN fragmentShaderHeader
+let ns = 4, cns = 4;
+fragmentShaderHeader+= 'const int ns = ' + ns + ';\n';
+let fragmentShaderDefs = 'const int cns = ' + cns + ';\n';
+let nfsh = fragmentShaderHeader.split('\n').length + 1; // NUMBER OF LINES OF CODE IN fragmentShaderHeader
 
 let isFirefox = navigator.userAgent.indexOf('Firefox') > 0;         // IS THIS THE FIREFOX BROWSER?
 let errorMsg = '';
@@ -138,14 +140,13 @@ function gl_start(canvas, vertexShader, fragmentShader) {           // START WEB
          };
 
          addshader(gl.VERTEX_SHADER, vertexShader);                         // Add the vertex and fragment shaders.
-         addshader(gl.FRAGMENT_SHADER, fragmentShaderHeader + fragmentShader);
+         addshader(gl.FRAGMENT_SHADER, fragmentShaderHeader +fragmentShaderDefs+ fragmentShader);
 
          gl.linkProgram(program);                                               // Link the program, report any errors.
          if (!gl.getProgramParameter(program, gl.LINK_STATUS))
             console.log('Could not link the shader program!');
          gl.useProgram(program);
          gl.program = program;
-         const ns = 2;
          for(let i = 0; i < ns; ++i){
             loadTexture(gl, './'+(i+1)+'.jpg', i); //Texture loading.
             textures[i] = i;
diff --git a/shader.frag b/shader.frag
index 04fa609..8f853c6 100644
--- a/shader.frag
+++ b/shader.frag
@@ -1,26 +1,31 @@
 
-vec3 foregroundColor = vec3(.0841, .5329, .9604);
+vec3 foregroundColor = vec3(.0841, .5329, .9604); 
 vec3 groundColor = vec3(.2, .3, .5);
 vec4 groundSpecular = vec4(.71, .71, .71, 10.);
 uniform float uTime;// TIME, IN SECONDS
 uniform int flags;
-uniform vec4 rot;
-uniform float dFL;
-//FLAGS 0-TEX, 1-RT, 2-CLOUD, 3-TEX_ROT
+//FLAGS 0-TEX, 1-RT, 2-MOVED, 3-FLASH, 4-TEX_ROT, 5-CLOUD
+
+uniform vec4 rot; //ROTATION VALUES USED TO CALCULATE TRANSFORMATION MATRIX
+//rot=[cosx, sinx, cosy, siny], x, y BING ROTATED ANGLE
+uniform float dFL; //DELTA on FOCAL LENGTH
+uniform vec3 fDir;//Flash light direction
 varying vec3 vPos;// -1 < vPos.x < +1
 // -1 < vPos.y < +1
 //      vPos.z == 0
 
-float fl=3.;
+float fl=3.;//ORIGINAL FOCAL LENGTH
 const float pi=3.14159265359;
-const int n_ref=6;
-const int ns=2;
+const float _2pi=2.*pi;
+const int n_ref=5; //<<=======***********************MAX NUMBER OF RAY TRACING RECURRSIONS. INCREASE IT IF YOUR GRAPHICS CARD CAN HANDLE.**************************** 
+//const int ns=4; ns is added from .js
 vec4 Sph[ns];
 uniform sampler2D uSampler[ns];
 vec3 Ambient[ns];
 vec3 Diffuse[ns];
 vec4 Specular[ns];
-struct Sphere{
+float ks[ns];
+struct Sphere{ //UPDATED SPHERE STRUCTURE THAT SUPPORTS TRANSPARENCY.(UNUSED)
    vec4 Pos;
    vec3 Ambient;
    vec3 Diffuse;
@@ -28,7 +33,7 @@ struct Sphere{
    int textureid;
    float ks, kt;
 };
-struct RT{
+struct RT{ //STACK FOR RECURSIVE RAY TRACING.
    vec3 color;
    float ks;
    // vec3 colorr;
@@ -45,24 +50,31 @@ float clampv(float val,float l,float h){
    return val<l?l:val>h?h:val;
 }
 void main(){
-   
    ////////////////////////////////////////////////
    //
    // HERE, FOR YOUR HOMEWORK, YOU CAN WRITE ANY
    // CODE YOU LIKDEFINE A COLOR FOR THIS FRAGMENT.
    
    // LIGHT DIRECTION AND COLOR
-   
+   //* I USED LDir AS LIGHT POSITION
+   //* I NORMALIZED IT AFTER GETTING THE 
+   //* DIRECTION BY SUBTRACTING IT FROM THE POINT
    vec3 LDir=vec3(.5,.5,.5);
    vec3 LCol=vec3(1.,1.,1.);
    
    // SPHERE
+   Sph[3]=vec4(.9*sin(uTime*.4),0.,.9*cos(uTime*.4),.25);
+   Sph[2]=vec4(.22*sin(uTime*1.2),0.05,.22*cos(uTime*1.2),.02);
+   Sph[0]=vec4(.45*sin(uTime),0.05*cos(uTime + 1.),.45*cos(uTime),.1);
+   Sph[1]=vec4(0.,0.,0.,.15);
    
-   Sph[0]=vec4(.5*sin(uTime),0.,.5*cos(uTime),.2);
-   Sph[1]=vec4(0.,0.,0.,.2);
-   
-   // SURFACE REFLECTANCE PROPERTIES
-   
+   // SURFACE REFLECTANCE PROPERTIES, can be transferred from .js
+   Ambient[3]=vec3(.1,.1,.1);// r,g,b
+   Diffuse[3]=vec3(.71,.71,.71);// r,g,b
+   Specular[3]=vec4(.71,.71,.71,10.);// r,g,b,power
+   Ambient[2]=vec3(.1,.05,.05);// r,g,b
+   Diffuse[2]=vec3(.71,.71,.71);// r,g,b
+   Specular[2]=vec4(.71,.71,.71,10.);// r,g,b,power
    Ambient[1]=vec3(.1,.05,.05);// r,g,b
    Diffuse[1]=vec3(1.,.5,.5);// r,g,b
    Specular[1]=vec4(1.,.5,.5,10.);// r,g,b,power
@@ -70,32 +82,37 @@ void main(){
    Ambient[0]=vec3(.05,.05,.1);// r,g,b
    Diffuse[0]=vec3(.5,.5,1.);// r,g,b
    Specular[0]=vec4(1.,.5,.5,20.);// r,g,b,power
-   
+   ks[0] = 0.25;
+   ks[1] = 0.1;
+   ks[2] = 0.3;
+   ks[3] = 0.05;
    // INITIALIZE TO A BACKGROUND COLOR
-   
    vec3 color=vec3(.2, .3, .5);
    float ca=rot.x, sa = rot.y, cb=rot.z, sb=rot.w;
-   // COMPUTE THE RAY ORIGIN AND DIRECTION
-   mat3 transformation, invTr;
-   transformation[0] = vec3(ca, sb*sa, sa*cb);
-   transformation[1] = vec3(0, cb, -sb);
-   transformation[2] = vec3(-sa,ca*sb,ca*cb);
-   invTr[0] = vec3(ca, 0, -sa);
+   mat3 transformation, invTr;//Transformation matrix for viewpoint.
+   transformation[0] = vec3(ca, sb*sa, sa*cb);//because the matrices are all the same,
+   transformation[1] = vec3(0, cb, -sb);//We don't need to calculate it for every pixel
+   transformation[2] = vec3(-sa,ca*sb,ca*cb);//So, we get it from the CPU
+   invTr[0] = vec3(ca, 0, -sa);//it's inverse, to calculate texture mapping.
    invTr[1] = vec3(sa*sb, cb, ca*sb);
    invTr[2] = vec3(cb*sa, -sb, ca*cb);
-
-   vec3 trPos = transformation*vec3(vPos.xy, -2);
-
-   vec3 V=transformation*vec3(0.,0.,fl+dFL);
+   vec3 trPos = transformation*((dFL+fl+1.)/(fl+1.))*vec3(vPos.xy, -1);
+   // COMPUTE THE RAY ORIGIN AND DIRECTION
+   vec3 V0=transformation*vec3(0.,0.,fl+dFL), V = V0;
    vec3 W=normalize(trPos-V);
    // RAY TRACE TO ALL OBJECTS IN THE SCENE
-   bool rtxoff = getflag(flags, 1);
+   bool rtxoff = getflag(flags, 1), 
+   showtexture = !getflag(flags,0), 
+   moved = getflag(flags,2)//,
+//   flash = true;//getflag(flags, 3)
+   ;//get flags.
+ //  bool hit = false;
    int cnt_ref = n_ref;
    for(int j=0;j<n_ref;j++)
    {
       float tMin=10000.;
       int iMin = -1;
-      for(int i=0;i<ns;i++){
+      for(int i=0;i<cns;i++){
          // SHIFT COORDINATES, SO THAT SPHERE IS AT (0,0,0)
          vec3 Vp=V-Sph[i].xyz;
          // SOLVE FOR QUADRATIC EQUATION IN t
@@ -105,8 +122,8 @@ void main(){
          if(D>0.){
             float t=-B-sqrt(D);
             if(t > 0. && t < tMin){
-               tMin = t;
-               iMin = i;
+               tMin = t; //This is an optimization, we don't have to do lighting/tex
+               iMin = i; // for objects that are occuluded, which is expensive!
             }
          }
       }
@@ -114,47 +131,61 @@ void main(){
       if(iMin >= 0){
          float t = tMin;
          vec3 S=V+t*W;
-         for(int i = 0; i < ns; ++ i)
-            if(i == iMin)
-            {
-               //*TEXTURE MAPPING
-               vec3 tex_sph=invTr*(S-Sph[i].xyz);
+         for(int i = 0; i < cns; ++ i)
+            if(i == iMin) //* Because GLSL doesn't support non-const index, 
+            {             //*  we have to get Sph[iMin], uSampler[iMin], etc. this way
+               //*Good old TEXTURE MAPPING from hw1
+               vec3 tex_sph = (S-Sph[i].xyz);
+               if(moved)
+                  tex_sph=invTr*tex_sph;//* transform the sphere to original place if view point moved;
+                                        //* This is super expensive! plus it's in the inner loop!!
+                                        //* We added a flag to disable it when the viewport is not moved!
                float R=Sph[i].w;
                float tex_x=acos(abs(tex_sph.x)/sqrt(R*R-tex_sph.y*tex_sph.y));
                if(tex_sph.x>0.)
                   tex_x=pi-tex_x;
-               tex_x=R*tex_x;
                tex_x*=1.5708;//*Correct aspect ratio of texture 2:1 -> 2pir:2r
-               tex_x=tex_x+float(uTime)*R;
-               float _2pir=2.*pi*R;
-               float quo=float(int(tex_x/_2pir));
-               tex_x=clampv((tex_x-quo*_2pir),0.,_2pir)/_2pir;
+               tex_x=tex_x+float(uTime);
+               float quo=float(int(tex_x/_2pi));
+               tex_x=tex_x/_2pi -quo;
                vec3 texture_color;
-               if(!getflag(flags,0))
+               if(showtexture)
                   texture_color=texture2D(uSampler[i],vec2(tex_x,((R-tex_sph.y)/(2.*R)))).xyz;
                else texture_color = foregroundColor;
                vec3 N=normalize(S-Sph[i].xyz);
                //*DIRECTIONS ARE NORMALIZED TO GET THE CORRECT PHONG LIGHTING
-               vec3 realLDir=normalize(LDir-S);
+               vec3 realLDir=normalize(LDir-S); 
                color=(
                      Ambient[i]
                      +Diffuse[i]*max(0.,dot(N,realLDir))*LCol
                   )*texture_color
                ;
                // + SPECULAR COMPONENT GOES HERE
-               if(rtxoff || j == n_ref - 1)
-                  color += sqrt(float(j+1)) * Specular[i].xyz*pow(max(0.,dot(2.*dot(N,realLDir)*N-realLDir,-W)),Specular[i].w);
-               stack[j] = RT(color, 0.15);
-               V = S;
-               W = -normalize(2. * dot(N, W) * N - W);
-               break;
+               if(rtxoff || j == n_ref - 1) //if it's the last ray
+                  color += sqrt(float(j+1)) * Specular[i].xyz*pow(max(0.,
+                  dot(2.*dot(N,realLDir)*N-realLDir,-W)),Specular[i].w);
+               //*Pushing current color and ks into stack.
+               //*suppose ks is 0.15 for all spheres, we can 
+               //*of course support different ks, kt for different object
+               //*but I didn't have time to do that, just a proof of concept,
+               //*I defined the new sphere structure that could be used in the future.
+               stack[j] = RT(color, ks[i]);
+               V = S; //*NEXT RAY SHOOTING FROM THE INTERSECTION POINT 
+               // if(flash && j == 0){
+               //    V0 = V - V0;
+               //    hit = true;
+               // }               
+               W = -normalize(2. * dot(N, W) * N - W);//*W is the next direction of the next ray.
+
+               break;// this is only the innerloop, RT is still going!
             }
       }
       else {
       // TO SIMIPIFY THINGS UP, I'LL ASSUME THAT EVERYTHING 
       // IS INSIDE THE BOUNDING BOX [(-1,-1,-1), (1,1,1)]
-      // AND THERE'S A FLOOR at [y = -1]
-
+      // AND THERE'S A FLOOR at [y = -1] THE NORMAL IS (0,1,0)
+      // Because We assumed that the light always hit sphere first,
+      // It will have wirld behavior when you rotate the scene upsidedown.
          float t = -(.2+V.y)/W.y;
          float sx = V.x + t* W.x, sz = V.z + t * W.z;
 
@@ -163,28 +194,32 @@ void main(){
             vec3 S = vec3(sx, -.2, sz);
             vec3 realLDir=normalize(LDir - S);
             color=(
-                  0.5
-                  +0.5*max(0.,realLDir.y)*LCol
+                  0.5 //ambient for ground
+                  +0.5*max(0.,realLDir.y)*LCol //diffusion for ground
                )*groundColor
             ;
             // + SPECULAR COMPONENT GOES HERE
             if(rtxoff || j == n_ref - 1)
-               color += sqrt(float(j+1))*groundSpecular.xyz*
+               color += sqrt(float(j+1))*groundSpecular.xyz* //specular for ground.
                   pow(max(0., dot(vec3(-realLDir.x, realLDir.y,-realLDir.z),-W)),groundSpecular.w);
-            stack[j] = RT(color, 0.1);
-            V = S;
-            W = vec3(W.x, -W.y, W.z);
+            stack[j] = RT(color, 0.15); //ks of ground is 0.1
+            V = S; //Same as above, trace again from S, dir = reflect(W, N).
+            // if(flash && j == 0){
+            //    V0 = W;
+            //    hit = true;
+            // }
+            W = vec3(W.x, -W.y, W.z); 
          }
          else{
             if(j > 0)
             {
+               // If the light bounces away! The color of it is calculated by 
                stack[j] = RT(sqrt(float(j+1))*vec3(4.,4.,4)*pow(max(0.,dot(W, normalize(LDir - V))), 10.), 0.);
                cnt_ref = j + 1;
             }
-            else
-               cnt_ref = j;
-
-            break;
+            else //If the light hits the void in the first place, it's just black!
+               cnt_ref = j;//j is always 0 in this case.
+            break; //The light is shooting into the void, let's stop RT.
          }
       }       
       // RTX off
@@ -199,9 +234,9 @@ void main(){
       float currks = 1.;
       for(int i = 0; i < n_ref; ++i)
       {
-         if(i >= cnt_ref)
+         if(i >= cnt_ref)//same trick to use bounded non-const on indexes
          {
-            color += currks * stack[i - 1].color;
+            color += currks * stack[i - 1].color; //if there're less than n_ref rays, e.g. ray go to the void.
             break;
          }
          color += currks *(1.-stack[i].ks) * stack[i].color;
@@ -211,6 +246,7 @@ void main(){
          color += currks * stack[n_ref - 1].color;
    }
    // APPLY GAMMA CORRECTION AND SET THE PIXEL COLOR.
+
    gl_FragColor=vec4(sqrt(color),1.);
 }
    
\ No newline at end of file
