diff --git a/Parameters_April21.md b/Parameters_April21.md
index 041c59f..1cdf8d4 100644
--- a/Parameters_April21.md
+++ b/Parameters_April21.md
@@ -79,11 +79,113 @@ Some parameters in early versions may be off, since not all versions were backed
 
 ### 29 April 21 - The dark side of the pool ###
 
-**Program:** `xxx.c`
+**Program:** `wave_billaird.c` (parameters reconstructed for 1 August version)
 
-**Initial condition in function `animation()`:** `xxx`
+**Initial condition in function `animation()`:** `init_wave(LAMBDA, 0.0, phi, psi, xy_in);`
 
 ```
+#define MOVIE 1         /* set to 1 to generate movie */
+
+/* General geometrical parameters */
+
+#define WINWIDTH 	1280  /* window width */
+#define WINHEIGHT 	720   /* window height */
+
+// #define NX 1280          /* number of grid points on x axis */
+// #define NY 720          /* number of grid points on y axis */
+#define NX 640          /* number of grid points on x axis */
+#define NY 360          /* number of grid points on y axis */
+
+/* setting NX to WINWIDTH and NY to WINHEIGHT increases resolution */
+/* but will multiply run time by 4                                 */
+
+#define XMIN -2.0
+#define XMAX 2.0	/* x interval */
+#define YMIN -1.125
+#define YMAX 1.125	/* y interval for 9/16 aspect ratio */
+
+#define JULIA_SCALE 1.0 /* scaling for Julia sets */
+
+/* Choice of the billiard table */
+
+#define B_DOMAIN 1      /* choice of domain shape, see list in global_pdes.c */
+
+#define CIRCLE_PATTERN 10    /* pattern of circles, see list in global_pdes.c */
+
+#define P_PERCOL 0.25       /* probability of having a circle in C_RAND_PERCOL arrangement */
+#define NPOISSON 300        /* number of points for Poisson C_RAND_POISSON arrangement */
+
+#define LAMBDA 1.5	    /* parameter controlling the dimensions of domain */
+#define MU 0.03	    /* parameter controlling the dimensions of domain */
+#define NPOLY 3             /* number of sides of polygon */
+#define APOLY 1.0           /* angle by which to turn polygon, in units of Pi/2 */ 
+#define MDEPTH 4            /* depth of computation of Menger gasket */
+#define MRATIO 3            /* ratio defining Menger gasket */
+#define MANDELLEVEL 1000      /* iteration level for Mandelbrot set */
+#define MANDELLIMIT 10.0     /* limit value for approximation of Mandelbrot set */
+#define FOCI 1              /* set to 1 to draw focal points of ellipse */
+#define NGRIDX 15            /* number of grid point for grid of disks */
+#define NGRIDY 20           /* number of grid point for grid of disks */
+
+/* You can add more billiard tables by adapting the functions */
+/* xy_in_billiard and draw_billiard below */
+
+/* Physical parameters of wave equation */
+
+#define TWOSPEEDS 0         /* set to 1 to replace hardcore boundary by medium with different speed */
+
+#define OMEGA 0.9           /* frequency of periodic excitation */
+#define COURANT 0.01       /* Courant number */
+#define COURANTB 0.0075      /* Courant number in medium B */
+#define GAMMA 0.0      /* damping factor in wave equation */
+#define GAMMA_SIDES 1.0e-4      /* damping factor on boundary */
+#define GAMMA_TOPBOT 1.0e-6      /* damping factor on boundary */
+#define KAPPA 0.0       /* "elasticity" term enforcing oscillations */
+#define KAPPA_SIDES 5.0e-4       /* "elasticity" term on absorbing boundary */
+#define KAPPA_TOPBOT 0.0       /* "elasticity" term on absorbing boundary */
+/* The Courant number is given by c*DT/DX, where DT is the time step and DX the lattice spacing */
+/* The physical damping coefficient is given by GAMMA/(DT)^2 */
+/* Increasing COURANT speeds up the simulation, but decreases accuracy */
+/* For similar wave forms, COURANT^2*GAMMA should be kept constant */
+
+/* Boundary conditions, see list in global_pdes.c  */
+
+#define B_COND 3
+
+/* Parameters for length and speed of simulation */
+
+#define NSTEPS 8000      /* number of frames of movie */
+#define NVID 40          /* number of iterations between images displayed on screen */
+#define NSEG 100         /* number of segments of boundary */
+#define INITIAL_TIME 0    /* time after which to start saving frames */
+#define BOUNDARY_WIDTH 3    /* width of billiard boundary */
+
+#define PAUSE 1000         /* number of frames after which to pause */
+#define PSLEEP 1         /* sleep time during pause */
+#define SLEEP1  1        /* initial sleeping time */
+#define SLEEP2  1   /* final sleeping time */
+
+/* Plot type, see list in global_pdes.c  */
+
+#define PLOT 0
+
+/* Color schemes */
+
+#define BLACK 0          /* background */
+
+#define COLOR_SCHEME 0   /* choice of color scheme, see list in global_pdes.c  */
+
+#define SCALE 0          /* set to 1 to adjust color scheme to variance of field */
+#define SLOPE 2.0        /* sensitivity of color on wave amplitude */
+#define ATTENUATION 0.0  /* exponential attenuation coefficient of contrast with time */
+#define E_SCALE 750.0     /* scaling factor for energy representation */
+
+#define COLORHUE 260     /* initial hue of water color for scheme C_LUM */
+#define COLORDRIFT 0.0   /* how much the color hue drifts during the whole simulation */
+#define LUMMEAN 0.5      /* amplitude of luminosity variation for scheme C_LUM */
+#define LUMAMP 0.3       /* amplitude of luminosity variation for scheme C_LUM */
+#define HUEMEAN 220.0    /* mean value of hue for color scheme C_HUE */
+#define HUEAMP -220.0      /* amplitude of variation of hue for color scheme C_HUE */
 
 ```