diff --git a/include/clock.h b/include/clock.h
index 77ab7e9..c12c41e 100644
--- a/include/clock.h
+++ b/include/clock.h
@@ -10,7 +10,6 @@
 
 /**
  * Sets HCLK (system clock) to 80MHz, the maximum.
- * @param none
  */
 extern void clock_init(void);
 
diff --git a/include/display.h b/include/display.h
index 6004f19..55f6974 100644
--- a/include/display.h
+++ b/include/display.h
@@ -1,18 +1,55 @@
+/*
+ * @file display.h
+ * Display library for ILI9481 display.
+ */
+
 #ifndef DISPLAY_H_
 #define DISPLAY_H_
 
 #include <stdint.h>
 
+/**
+ * The screen's width, in pixels.
+ */
 #define LCD_WIDTH  480
-#define LCD_HEIGHT 320
 
-#define COLOR_MAX 31
+/**
+ * The screen's height, in pixels.
+ */
+#define LCD_HEIGHT 320
 
+/**
+ * Returns the color integer for the given RGB values.
+ * Converts 8RGB to 5-6-5.
+ * @param r red value, 0-255
+ * @param g green value, 0-255
+ * @param b blue value, 0-255
+ * @return the 5-6-5 color value
+ */
 uint16_t dsp_color(uint8_t r, uint8_t g, uint8_t b);
 
+/**
+ * Sets the direction of IO, for reading or writing to the screen.
+ * @param mode INPUT or OUPUT (defined in gpio.h)
+ */
 void dsp_dmode(int mode);
+
+/**
+ * Writes the command byte to the display.
+ * @param data the command to write
+ */
 void dsp_write_cmd(uint8_t data);
+
+/**
+ * Writes the data byte to the display.
+ * @param data the data to write
+ */
 void dsp_write_data(uint8_t data);
+
+/**
+ * Reads a byte of data from the display.
+ * @return the data byte
+ */
 uint8_t dsp_read_data(void);
 
 void dsp_set_addr(uint16_t x1, uint16_t y1, uint16_t x2, uint16_t y2);
diff --git a/include/display_draw.h b/include/display_draw.h
index 823c697..9d86437 100644
--- a/include/display_draw.h
+++ b/include/display_draw.h
@@ -1,16 +1,65 @@
+/**
+ * @file display_draw.h
+ * Provides functions for drawing to the display
+ */
+
 #ifndef DISPLAY_DRAW_H_
 #define DISPLAY_DRAW_H_
 
 #include <stdint.h>
 
+/**
+ * Starts the task for a blinking text cursor.
+ */
 void dsp_cursoron(void);
 
+/**
+ * Sets the chosen pixel to the given color.
+ * @param x x-coord of the pixel
+ * @param y y-coord of the pixel
+ * @param color the color to use (5-6-5)
+ */
 void dsp_pixel(int x, int y, uint16_t color);
+
+/**
+ * Draws a line between the two coordinates.
+ * @param x start x-coord
+ * @param y start y-coord
+ * @param i end x-coord
+ * @param j end y-coord
+ * @param color the color to use (5-6-5)
+ */
 void dsp_line(int x, int y, int i, int j, uint16_t color);
+
+/**
+ * Draws a rectangle with the given dimensions.
+ * @param x top left x-coord
+ * @param y top left y-coord
+ * @param w width of the rectangle
+ * @param h height of the rectangle
+ * @param color the color to use (5-6-5)
+ */
 void dsp_rect(int x, int y, int w, int h, uint16_t color);
 
+/**
+ * Sets the text cursor's position, in characters NOT pixels.
+ * @param x text column to move to
+ * @param y text row to move to
+ */
 void dsp_cpos(int x, int y);
+
+/**
+ * Sets the pixel offset of the text cursor.
+ * @param x x-pixel offset from (0, 0)
+ * @param y y-pixel offset from (0, 0)
+ */
 void dsp_coff(int x, int y);
+
+/**
+ * Puts a string to the screen. Text position if kept track of internally, so
+ * multiple calls will print the strings in one line.
+ * @param s the string to print
+ */
 void dsp_puts(const char *s);
 
 #endif // DISPLAY_DRAW_H_
diff --git a/include/it b/include/it
index 7c2b8d4..a9d20d8 120000
--- a/include/it
+++ b/include/it
@@ -1 +1 @@
-../../interpreter
\ No newline at end of file
+../../interpreter3
\ No newline at end of file
diff --git a/include/script.h b/include/script.h
index 7901c9c..ab5fa7e 100644
--- a/include/script.h
+++ b/include/script.h
@@ -12,6 +12,6 @@
  * Loads the library for the given interpreter.
  * @param it the interpreter to use
  */
-void script_loadlib(interpreter *it);
+void script_loadlib(instance *it);
 
 #endif // SCRIPT_H_
diff --git a/initrd/init b/initrd/init
index 4908747..3379d81 100644
--- a/initrd/init
+++ b/initrd/init
@@ -1,69 +1,67 @@
 # graph area
-set plotx 50
-set ploty 50
-set plotw 380
-set ploth 220
-set cx (plotx + (plotw / 2))
-set cy (ploty + (ploth / 2))
+plotx = 50
+ploty = 50
+plotw = 380
+ploth = 220
+cx = plotx + plotw / 2
+cy = ploty + ploth / 2
 
 # graph range
-set xmin (0 - 10)
-set xmax 10
-set ymin (0 - 10)
-set ymax 10
+xmin = 0 - 10
+xmax = 10
+ymin = 0 - 10
+ymax = 10
 
-set xinc (plotw / (xmax - xmin))
-set yinc (ploth / (ymax - ymin))
+xinc = plotw / (xmax - xmin)
+yinc = ploth / (ymax - ymin)
 
-color 3 3 3 > mlines
+mlines = color(3, 3, 3)
 
-# print axis
+func(makegrid) {
+	rect(plotx, ploty, plotw, ploth, 0)
 
-func makegrid
-	rect plotx ploty plotw ploth 0
+	x = plotx
+	while (x <= plotx + plotw) {
+		line(x, ploty, x, ploty + ploth, mlines)
+		x = x + xinc
+	}
 
-	set x plotx
-	do
-		line x ploty x (ploty + ploth) mlines
-		set x (x + xinc)
-	while (x <= plotx + plotw)
+	y = ploty
+	while (y <= ploty + ploth) {
+		line(plotx, y, plotx + plotw, y, mlines)
+		y = y + yinc
+	}
 
-	set y ploty
-	do
-		line plotx y (plotx + plotw) y mlines
-		set y (y + yinc)
-	while (y <= ploty + ploth)
-
-	line cx ploty cx (ploty + ploth) 32767
-	line plotx cy (plotx + plotw) cy 32767
-end
+	line(cx, ploty, cx, ploty + ploth, 32767)
+	line(plotx, cy, plotx + plotw, cy, 32767)
+}
 
 #
 # BIG LOOP - ask for equ, graph it
 #
 
-makegrid
-set clearcmd "clear"
-do
-	rect 0 0 480 40
-
-	print "f(x) = "
-	gets > Fx
+makegrid()
+clearcmd = "clear"
+while (1) {
+	rect(0, 0, 480, 40, 0)
+	print("f(x) = ")
+	Fx = gets()
 
-	if (Fx == clearcmd)
-		makegrid
-	else
+	if (Fx == clearcmd) {
+		makegrid()
+	} else {
 		# do function
-		set x xmin
-		do
-			solve Fx > y
-			set y (0 - y)
-			if ((y >= ymin) & (y <= ymax))
-				pixel (cx + x * xinc) (cy + y * yinc) 511
-			end
-			set x (x + 1 / xinc)
-		while (x < xmax)
-	end
+		x = xmin
+		while (x < xmax) {
+			y = solve(Fx)
+			y = 0 - y
+			if ((y >= ymin) & (y <= ymax)) {
+				pixel(cx + x * xinc, cy + y * yinc, 511)
+			}
+			x = x + 1 / xinc
+		}
+	}
+
+	ppos(0, 0)
+}
 
-	ppos 0 0
-while (1)
diff --git a/libinterp.a b/libinterp.a
index 11ca083..36331ee 100644
Binary files a/libinterp.a and b/libinterp.a differ
diff --git a/src/heap.c b/src/heap.c
index 52b5253..9a11cba 100644
--- a/src/heap.c
+++ b/src/heap.c
@@ -76,6 +76,8 @@ void free(void *buf)
 		return;
 
 	alloc_t *alloc = (alloc_t *)((uint8_t *)buf - sizeof(alloc_t));
+	if (alloc->next != 0)
+		return;
 	heap_used -= alloc->size;
 	alloc->next = free_blocks;
 	free_blocks = alloc;
diff --git a/src/main.c b/src/main.c
index 71ce68f..fc64edd 100644
--- a/src/main.c
+++ b/src/main.c
@@ -82,9 +82,8 @@ void kmain(void)
 
 void task_interpreter(void)
 {
-	interpreter it;
-	iinit(&it);
-	script_loadlib(&it);
+	instance *it = inewinstance();
+	script_loadlib(it);
 
 	char *s = initrd_getfile("init");
 	if (s == 0) {
@@ -105,7 +104,7 @@ void task_interpreter(void)
 		}
 		strncpy(linebuf, s + prev, lc + 1);
 		linebuf[lc] = '\0';
-		ret = idoline(&it, linebuf);
+		ret = idoline(it, linebuf);
 		if (ret < 0)
 			break;
 		prev = ++i;
diff --git a/src/script.c b/src/script.c
index 8fad2f3..1cd0d71 100644
--- a/src/script.c
+++ b/src/script.c
@@ -7,23 +7,25 @@
 #include <heap.h>
 #include <random.h>
 #include <serial.h>
-#include <stack.h>
+#include <stdlib.h>
 #include <keypad.h>
 
 #include <string.h>
 
-int script_puts(interpreter *it);
-int script_gets(interpreter *it);
-int script_delay(interpreter *it);
-int script_rect(interpreter *it);
-int script_ppos(interpreter *it);
-int script_line(interpreter *it);
-int script_color(interpreter *it);
-int script_rand(interpreter *it);
-int script_getkey(interpreter *it);
-int script_pixel(interpreter *it);
-
-void script_loadlib(interpreter *it)
+#define igetarg_integer(it, n) ((int)igetarg(it, n)->value.f)
+
+int script_puts(instance *it);
+int script_gets(instance *it);
+int script_delay(instance *it);
+int script_rect(instance *it);
+int script_ppos(instance *it);
+int script_line(instance *it);
+int script_color(instance *it);
+int script_rand(instance *it);
+int script_getkey(instance *it);
+int script_pixel(instance *it);
+
+void script_loadlib(instance *it)
 {
 	inew_cfunc(it, "print", script_puts);
 	inew_cfunc(it, "gets", script_gets);
@@ -37,14 +39,20 @@ void script_loadlib(interpreter *it)
 	inew_cfunc(it, "pixel", script_pixel);
 }
 
-int script_puts(interpreter *it)
+int script_puts(instance *it)
 {
-	const char *s = igetarg_string(it, 0);
-	dsp_puts(s);
+	variable *v = igetarg(it, 0);
+	if (v->type == NUMBER) {
+		char buf[33];
+		snprintf(buf, 33, "%f", v->value.f);
+		dsp_puts(buf);
+	} else if (v->type == STRING) {
+		dsp_puts((const char *)v->value.p);
+	}
 	return 0;
 }
 
-int script_gets(interpreter *it)
+int script_gets(instance *it)
 {
 	char *s = malloc(64);
 	char c[2] = {0, 0};
@@ -66,20 +74,19 @@ int script_gets(interpreter *it)
 	s[index] = '\0';
 
 	variable *r = make_vars(0, s);
-	iret(it, r);
+	ipush(it, (uint32_t)r);
 	free(s);
-	free(r);
 	return 0;
 }
 
-int script_delay(interpreter *it)
+int script_delay(instance *it)
 {
-	int ms = igetarg_integer(it, 0);
+	int ms = (int)igetarg(it, 0)->value.f;
 	delay(ms);
 	return 0;
 }
 
-int script_rect(interpreter *it)
+int script_rect(instance *it)
 {
 	dsp_rect(igetarg_integer(it, 0), igetarg_integer(it, 1),
 		igetarg_integer(it, 2), igetarg_integer(it, 3),
@@ -87,7 +94,7 @@ int script_rect(interpreter *it)
 	return 0;
 }
 
-int script_line(interpreter *it)
+int script_line(instance *it)
 {
 	int x = igetarg_integer(it, 0);
 	int y = igetarg_integer(it, 1);
@@ -98,42 +105,42 @@ int script_line(interpreter *it)
 	return 0;
 }
 
-int script_ppos(interpreter *it)
+int script_ppos(instance *it)
 {
 	dsp_cpos(0, 0);
 	dsp_coff(igetarg_integer(it, 0), igetarg_integer(it, 1));
 	return 0;
 }
 
-int script_color(interpreter *it)
+int script_color(instance *it)
 {
 	uint16_t c = dsp_color(igetarg_integer(it, 0), igetarg_integer(it, 1),
 		igetarg_integer(it, 2));
-	variable *v = make_varn(0, (float)c);
-	iret(it, v);
+	variable *v = make_varf(0, (float)c);
+	ipush(it, (uint32_t)v);
 	free(v);
 	return 0;
 }
 
-int script_rand(interpreter *it)
+int script_rand(instance *it)
 {
 	unsigned int mod = igetarg_integer(it, 0);
 	unsigned int val = random_get();
-	variable *v = make_varn(0, (float)(mod % val));
-	iret(it, v);
+	variable *v = make_varf(0, (float)(mod % val));
+	ipush(it, (uint32_t)v);
 	free(v);
 	return 0;
 }
 
-int script_getkey(interpreter *it)
+int script_getkey(instance *it)
 {
-	variable *v = make_varn(0, (float)keypad_get());
-	iret(it, v);
+	variable *v = make_varf(0, (float)keypad_get());
+	ipush(it, (uint32_t)v);
 	free(v);
 	return 0;
 }
 
-int script_pixel(interpreter *it)
+int script_pixel(instance *it)
 {
 	dsp_pixel(igetarg_integer(it, 0), igetarg_integer(it, 1),
 		igetarg_integer(it, 2));