diff --git a/initrd/init b/initrd/init
index a250822..4908747 100644
--- a/initrd/init
+++ b/initrd/init
@@ -58,7 +58,7 @@ do
 		do
 			solve Fx > y
 			set y (0 - y)
-			if ((y > ymin) & (y < ymax))
+			if ((y >= ymin) & (y <= ymax))
 				pixel (cx + x * xinc) (cy + y * yinc) 511
 			end
 			set x (x + 1 / xinc)
diff --git a/libinterp.a b/libinterp.a
index 2d0400d..11ca083 100644
Binary files a/libinterp.a and b/libinterp.a differ
diff --git a/src/display_draw.c b/src/display_draw.c
index 62578e3..f58dda7 100644
--- a/src/display_draw.c
+++ b/src/display_draw.c
@@ -39,10 +39,15 @@ void dsp_putchar(int c)
 		if (++cury == 12) {
 			UNLOCK;
 			dsp_rect(0, 0, LCD_WIDTH, LCD_HEIGHT, 0);
-			LOCK;
 			cury = 0;
 		}
 		return;
+	} else if (c == '\b') {
+		if (curx > 0)
+			curx--;
+		UNLOCK;
+		dsp_rect(curxo + curx * 12, curyo + cury * 26, 12, 26, 0);
+		return;
 	}
 
 	unsigned int start = ((c - ' ') / 16 * 192 * 26 + (c % 16) * 12) * 2;
diff --git a/src/heap.c b/src/heap.c
index 92978b7..52b5253 100644
--- a/src/heap.c
+++ b/src/heap.c
@@ -1,7 +1,6 @@
 #include <heap.h>
-#include <task.h>
 
-#define HEAP_ALIGN 16
+#define HEAP_ALIGN 4
 
 typedef struct {
 	uint32_t size;
@@ -10,7 +9,7 @@ typedef struct {
 
 static alloc_t *free_blocks;
 static void *heap_end;
-static uint32_t heap_used;
+uint32_t heap_used;
 
 void heap_init(void *buf)
 {
@@ -21,17 +20,29 @@ void heap_init(void *buf)
 
 void *malloc(uint32_t size)
 {
-	//task_hold(1);
 	size = (size + sizeof(alloc_t) + HEAP_ALIGN) & ~(HEAP_ALIGN - 1);
 
 	alloc_t *node = free_blocks;
 	alloc_t *prev = 0;
 	while (node != 0) {
 		if (node->size >= size) {
-			if (prev != 0)
-				prev->next = node->next;
-			else
-				free_blocks = node->next;
+			/*if (node->size > size + sizeof(alloc_t) + HEAP_ALIGN) {
+				alloc_t *rem = (alloc_t *)((uint8_t *)node +
+					sizeof(alloc_t) + size);
+				rem->size = node->size - size - sizeof(alloc_t);
+				rem->next = node->next;
+				if (prev != 0)
+					prev->next = rem;
+				else
+					free_blocks = rem;
+				node->size = size;
+			} else {*/
+				if (prev != 0)
+					prev->next = node->next;
+				else
+					free_blocks = node->next;
+			//}
+
 			node->next = 0;
 			heap_used += node->size;
 			return (void *)((uint8_t *)node + sizeof(alloc_t));
@@ -48,7 +59,6 @@ void *malloc(uint32_t size)
 	heap_end = (void *)((uint8_t *)heap_end + size);
 	heap_used += size;
 
-	//task_hold(0);
 	return (void *)((uint8_t *)node + sizeof(alloc_t)); 
 }
 
diff --git a/src/script.c b/src/script.c
index 495e409..8fad2f3 100644
--- a/src/script.c
+++ b/src/script.c
@@ -22,7 +22,6 @@ int script_color(interpreter *it);
 int script_rand(interpreter *it);
 int script_getkey(interpreter *it);
 int script_pixel(interpreter *it);
-int script_solve(interpreter *it);
 
 void script_loadlib(interpreter *it)
 {
@@ -36,7 +35,6 @@ void script_loadlib(interpreter *it)
 	inew_cfunc(it, "rand", script_rand);
 	inew_cfunc(it, "getkey", script_getkey);
 	inew_cfunc(it, "pixel", script_pixel);
-	inew_cfunc(it, "solve", script_solve);
 }
 
 int script_puts(interpreter *it)
@@ -50,14 +48,21 @@ int script_gets(interpreter *it)
 {
 	char *s = malloc(64);
 	char c[2] = {0, 0};
-	uint16_t index = 0;
+	int index = 0;
 
 	do {
 		c[0] = serial_get();
 		s[index] = c[0];
-		if (c[0] != '\r')
+		if (c[0] == '\b' || c[0] == 127) {
+			index--;
+			if (index > -1) {
+				dsp_puts("\b");
+				index--;
+			}
+		} else if (c[0] != '\r') {
 			dsp_puts(c);
-	} while (s[index] != '\r' && index++ < 23);
+		}
+	} while (s[index] != '\r' && index++ < 63);
 	s[index] = '\0';
 
 	variable *r = make_vars(0, s);
@@ -135,18 +140,3 @@ int script_pixel(interpreter *it)
 	return 0;
 }
 
-int script_solve(interpreter *it)
-{
-	const char *expr = igetarg_string(it, 0);
-	int len = strlen(expr);
-	char *buf = (char *)malloc(len + 2);
-	strcpy(buf, expr);
-	buf[len] = ')';
-	buf[len + 1] = '\0';
-	variable *r = idoexpr(it, buf);
-	if (r == 0)
-		r = make_varn(0, 0.0f);
-	iret(it, r);
-	free(r);
-	return 0;
-}
diff --git a/src/stdlib.c b/src/stdlib.c
index ec67ff3..e34d2a0 100644
--- a/src/stdlib.c
+++ b/src/stdlib.c
@@ -67,15 +67,49 @@ float strtof(const char *s, char **endptr)
 {
 	(void)s;
 	(void)endptr;
-	return 0.0f;
+
+	float res = 0.0f;
+	char neg = 0;
+	unsigned int i = 0;
+
+	if (s[0] == '-') {
+		neg = 1;
+		i++;
+	}
+
+	for (; isdigit(s[i]); i++) {
+		res *= 10.0f;
+		res += (s[i] - '0');
+	}
+
+	if (s[i] != '.')
+		goto end;
+
+	float div = 0.1f;
+	for (i++; isdigit(s[i]); i++) {
+		res += div * (s[i] - '0');
+		div /= 10.0f;
+	}
+
+end:
+	return (neg == 0) ? res : -res;
 }
 
 int atoi(const char *s)
 {
+	unsigned int i = 0;
+	char neg = 0;
 	int n = 0;
-	for (unsigned int i = 0; isdigit(s[i]); i++) {
+
+	if (s[0] == '-') {
+		neg = 1;
+		i = 1;
+	}
+
+	for (; isdigit(s[i]); i++) {
 		n *= 10;
 		n += s[i] - '0';
 	}
-	return n;
+
+	return (neg == 0) ? n : -n;
 }
diff --git a/src/stm32l4xx_it.c b/src/stm32l4xx_it.c
index e54a192..228dc67 100644
--- a/src/stm32l4xx_it.c
+++ b/src/stm32l4xx_it.c
@@ -12,12 +12,16 @@ void serial_puts(const char *s)
 
 void perror(const char *s)
 {
-	//extern task_t *current;
+	extern uint32_t heap_used;
 	serial_puts(s);
-	//char buf[200];
-	//snprintf(buf, 200, "xPSR: %x\r\nPC: %x\r\nLR: %x\r\n", current->sp[0],
-	//	current->sp[1], current->sp[2]);
-	//serial_puts(buf);
+
+	static char buf[200];
+	uint32_t *psp;
+	asm("mrs %0, psp" : "=r"(psp));
+
+	snprintf(buf, 200, "\r\nPC: %x\r\nLR: %x\r\nmemused: %db\r\n",
+		psp[6], psp[5], heap_used);
+	serial_puts(buf);
 }
 
 __attribute__ ((naked))