diff --git a/lambda-test/Makefile b/lambda-test/Makefile
index 7e0e6c8..7f1da67 100644
--- a/lambda-test/Makefile
+++ b/lambda-test/Makefile
@@ -21,7 +21,7 @@
 ## Here you can link to one more directory (and multiple .c files)
 EXTRA_SOURCE_DIR = ../lambda/
 EXTRA_SOURCE_FILES = interrupts.c adc.c sensors.c integers.c \
-lcdroutines.c display.c alert.c command.c strings.c usart.c
+lcdroutines.c display.c alert.c command.c strings.c usart.c rules.c
 
 ##########------------------------------------------------------##########
 ##########                 Programmer Defaults                  ##########
@@ -31,7 +31,7 @@
 
 PROGRAMMER_TYPE = avrisp
 # extra arguments to avrdude: baud rate, chip type, -F flag, etc.
-PROGRAMMER_ARGS = -b 19200 -P /dev/ttyACM3
+PROGRAMMER_ARGS = -b 19200 -P /dev/ttyACM0
 
 ##########------------------------------------------------------##########
 ##########                   Makefile Magic!                    ##########
diff --git a/lambda-test/avrjunit.c b/lambda-test/avrjunit.c
index 6215c49..4253c8e 100644
--- a/lambda-test/avrjunit.c
+++ b/lambda-test/avrjunit.c
@@ -34,9 +34,10 @@
 		char cbuf[24];
 		char nbuf[64];
 		char tcbuf[128];
-		// TODO use strncat_P (macro?)
-		strcpy_P(cbuf, (PGM_P)pgm_read_word(&(class.tests[i].class)));
-		strcpy_P(nbuf, (PGM_P)pgm_read_word(&(class.tests[i].name)));
+		strncpy_P(cbuf, (PGM_P)pgm_read_word(&(class.tests[i].class)),
+				sizeof(cbuf));
+		strncpy_P(nbuf, (PGM_P)pgm_read_word(&(class.tests[i].name)),
+				sizeof(nbuf));
 		snprintf(tcbuf, sizeof(tcbuf),
 				"<testcase classname=\"%s\" name=\"%s\">\n", cbuf, nbuf);
 		printString(tcbuf);
diff --git a/lambda-test/display-test.c b/lambda-test/display-test.c
index 3e2331a..757d6fd 100644
--- a/lambda-test/display-test.c
+++ b/lambda-test/display-test.c
@@ -101,7 +101,7 @@
 
 	updatePending = false;
 
-	resetMeas();
+	resetDisplay();
 	// reset max measurements
 	assertTrue(measMax.tempI == 0);
 	assertTrue(measMax.tempO == 0);
diff --git a/lambda-test/sensors-test.c b/lambda-test/sensors-test.c
index ac878df..2df4ae3 100644
--- a/lambda-test/sensors-test.c
+++ b/lambda-test/sensors-test.c
@@ -15,6 +15,7 @@
 #include "adc.h"
 #include "sensors.h"
 #include "pins.h"
+#include "messages.h"
 
 static TableEntry const testTable[] = {
 		{10, 10},
@@ -127,21 +128,21 @@
 bool testToInfoLean(void) {
 	char* info = toInfo(191);
 
-	return ! strcmp(info, LEAN);
+	return ! strcmp(info, MSG_LEAN);
 }
 
 bool testToInfoOkay(void) {
-	assertTrue(0 == strcmp(toInfo(190), OKAY));
-	assertTrue(0 == strcmp(toInfo(170), OKAY));
-	assertTrue(0 == strcmp(toInfo(151), OKAY));
+	assertTrue(0 == strcmp(toInfo(190), MSG_OKAY));
+	assertTrue(0 == strcmp(toInfo(170), MSG_OKAY));
+	assertTrue(0 == strcmp(toInfo(151), MSG_OKAY));
 
 	return true;
 }
 
 bool testToInfoIdeal(void) {
-	assertTrue(0 == strcmp(toInfo(150), IDEAL));
-	assertTrue(0 == strcmp(toInfo(140), IDEAL));
-	assertTrue(0 == strcmp(toInfo(130), IDEAL));
+	assertTrue(0 == strcmp(toInfo(150), MSG_IDEAL));
+	assertTrue(0 == strcmp(toInfo(140), MSG_IDEAL));
+	assertTrue(0 == strcmp(toInfo(130), MSG_IDEAL));
 
 	return true;
 }
@@ -149,7 +150,7 @@
 bool testToInfoRich(void) {
 	char* info = toInfo(129);
 
-	return ! strcmp(info, RICH);
+	return ! strcmp(info, MSG_RICH);
 }
 
 /* Test "class" */
diff --git a/lambda/Makefile b/lambda/Makefile
index 0394c6b..b34ace8 100644
--- a/lambda/Makefile
+++ b/lambda/Makefile
@@ -15,7 +15,7 @@
 ## If you've split your program into multiple .c / .h files, 
 ## include the additional source (in same directory) here 
 LOCAL_SOURCE = usart.c interrupts.c adc.c sensors.c integers.c lcdroutines.c \
-display.c alert.c command.c strings.c
+display.c alert.c command.c strings.c rules.c
 
 ## Here you can link to one more directory (and multiple .c files)
 EXTRA_SOURCE_DIR = 
@@ -29,7 +29,7 @@
 
 PROGRAMMER_TYPE = avrisp
 # extra arguments to avrdude: baud rate, chip type, -F flag, etc.
-PROGRAMMER_ARGS = -b 19200 -P /dev/ttyACM3
+PROGRAMMER_ARGS = -b 19200 -P /dev/ttyACM0
 
 ##########------------------------------------------------------##########
 ##########                   Makefile Magic!                    ##########
diff --git a/lambda/TODO b/lambda/TODO
index 54e5991..a5a43b3 100644
--- a/lambda/TODO
+++ b/lambda/TODO
@@ -6,7 +6,7 @@
 - What happens if USART data is sent to the AVR too fast (GtkTerm Send Raw File)
 
 * Functionality
-- Add rules and alerts according to FIRE RULEZ!
+- Implement i18n
   
 * Circuit
 - Look at oxygen sensor voltage with voltmeter/oscilloscope - is the voltage
diff --git a/lambda/alert.c b/lambda/alert.c
index 1b7e7f6..f205339 100644
--- a/lambda/alert.c
+++ b/lambda/alert.c
@@ -8,8 +8,6 @@
  *
  */
 
-#include <stdio.h>
-#include <stdbool.h>
 #include <avr/io.h>
 #include "integers.h"
 #include "alert.h"
@@ -51,7 +49,7 @@
 }
 
 void alert(uint8_t const beeps, uint8_t const length, uint16_t const tone,
-		char* const line0, char* const line1) {
+		const char* const line0, const char* const line1) {
 	OCR1A = tone;
 	if (TCNT1 >= tone) TCNT1 = 0;
 	alertActive = true;
@@ -61,6 +59,16 @@
 	displayText(line0, line1);
 }
 
+void alert_P(uint8_t const beeps, uint8_t const length, uint16_t const tone,
+		PGM_P const line0_P, PGM_P const line1_P) {
+	char line0[17];
+	char line1[17];
+	strncpy_P(line0, line0_P, sizeof(line0));
+	strncpy_P(line1, line1_P, sizeof(line1));
+
+	alert(beeps, length, tone, line0, line1);
+}
+
 void cancelAlert(void) {
 	beepCount = 0;
 	oscCount = 0;
diff --git a/lambda/alert.h b/lambda/alert.h
index 0bc8b61..20b4e95 100644
--- a/lambda/alert.h
+++ b/lambda/alert.h
@@ -11,6 +11,10 @@
 #ifndef ALERT_H_
 #define ALERT_H_
 
+#include <avr/pgmspace.h>
+#include <stdbool.h>
+#include <stdio.h>
+
 void oscillateBeep(void);
 
 /**
@@ -25,7 +29,14 @@
  * respectively.
  */
 void alert(uint8_t beeps, uint8_t length, uint16_t tone,
-		char* line0, char* line1);
+		const char* line0, const char* line1);
+
+/**
+ * Like alert(), but line0_P and line1_P are expected to be static pointers to
+ * strings stored in program space like so: PSTR("string").
+ */
+void alert_P(uint8_t beeps, uint8_t length, uint16_t tone,
+		PGM_P line0_P, PGM_P line1_P);
 
 /**
  * Stops beeping and blocking display updates.
diff --git a/lambda/command.c b/lambda/command.c
index d463ee4..5aee933 100644
--- a/lambda/command.c
+++ b/lambda/command.c
@@ -19,6 +19,7 @@
 #include "alert.h"
 #include "command.h"
 #include "strings.h"
+#include "rules.h"
 
 static bool simulation = false;
 static bool logging = false;
@@ -37,13 +38,15 @@
 	split(data, " ", fields, fieldCount);
 	if (strcmp_P(fields[0], PSTR("se")) == 0) {
 		// simulation enable
-		resetMeas();
+		resetDisplay();
+		resetRules();
 		simulation = true;
 		beep(1, 2, 31);
 	}
 	else if (strcmp_P(fields[0], PSTR("sd")) == 0) {
 		// simulation disable
-		resetMeas();
+		resetDisplay();
+		resetRules();
 		simulation = false;
 		beep(1, 2, 31);
 	}
@@ -82,6 +85,7 @@
 	else if (simulation) {
 		Measurement meas = readMeas(fields, fieldCount);
 		updateMeas(meas);
+		reason(meas);
 	}
 }
 
diff --git a/lambda/display.c b/lambda/display.c
index b371378..26a3db4 100644
--- a/lambda/display.c
+++ b/lambda/display.c
@@ -11,6 +11,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <avr/interrupt.h>
 #include <util/delay.h>
 #include "usart.h"
@@ -21,12 +22,26 @@
 
 #define MENU_OFF 0
 #define MENU_MAX_VALUES 1
+#define MENU_LAST_TEXT 2
 
 uint8_t position = MENU_OFF;
 bool updatePending = false;
 Measurement measLatest = {0, 0, 0};
 Measurement measMax = {0, 0, 2000};
 
+static char lastLine0[17];
+static char lastLine1[17];
+
+/**
+ * Sets the given two lines of text on the display.
+ */
+static void setText(const char* const line0, const char* const line1) {
+	lcd_setcursor(0, 1);
+	lcd_string(line0);
+	lcd_setcursor(0, 2);
+	lcd_string(line1);
+}
+
 /**
  * Formats the given measurement values and displays them on an 16x2 LCD along
  * with the given hint.
@@ -40,10 +55,7 @@
 	snprintf(line0, sizeof(line0), "Ti %3dC To %3dC ", meas.tempI, meas.tempO);
 	snprintf(line1, sizeof(line1), "L  %d.%02d %s %s",
 			lambdaT.quot, abs(lambdaT.rem), toInfo(lambdax100), hint);
-	lcd_setcursor(0, 1);
-	lcd_string(line0);
-	lcd_setcursor(0, 2);
-	lcd_string(line1);
+	setText(line0, line1);
 }
 
 void cycleDisplay(void) {
@@ -54,9 +66,14 @@
 		return;
 	}
 	position++;
-	if (position > MENU_MAX_VALUES) {
+	if (position > MENU_LAST_TEXT ||
+			(position == MENU_LAST_TEXT &&
+			 strlen(lastLine0) == 0 && strlen(lastLine1) == 0)) {
 		position = MENU_OFF;
 	}
+	if (position == MENU_LAST_TEXT) {
+		lcd_clear();
+	}
 	beep(1, 2, 31);
 }
 
@@ -70,7 +87,7 @@
 	updatePending = true;
 }
 
-void resetMeas(void) {
+void resetDisplay(void) {
 	measMax.tempI = 0;
 	measMax.tempO = 0;
 	measMax.lambda = 2000;
@@ -84,6 +101,8 @@
 
 		if (position == MENU_MAX_VALUES) {
 			displayMeas(measMax, "|>");
+		} else if (position == MENU_LAST_TEXT) {
+			setText(lastLine0, lastLine1);
 		} else {
 			displayMeas(measLatest, "  ");
 		}
@@ -98,10 +117,11 @@
 	printString(log);
 }
 
-void displayText(char* const line0, char* const line1) {
+void displayText(const char* const line0, const char* const line1) {
+	lastLine0[0] = '\0';
+	lastLine1[0] = '\0';
+	strncat(lastLine0, line0, sizeof(lastLine0) - 1);
+	strncat(lastLine1, line1, sizeof(lastLine1) - 1);
 	lcd_clear();
-	lcd_setcursor(0, 1);
-	lcd_string(line0);
-	lcd_setcursor(0, 2);
-	lcd_string(line1);
+	setText(line0, line1);
 }
diff --git a/lambda/display.h b/lambda/display.h
index 969c395..0d1ff09 100644
--- a/lambda/display.h
+++ b/lambda/display.h
@@ -29,7 +29,7 @@
 /**
  * Resets max measurements to initial values and flags pending display update.
  */
-void resetMeas(void);
+void resetDisplay(void);
 
 /**
  * Updates the display if an update is pending.
@@ -44,6 +44,6 @@
 /**
  * Displays the given two lines of text.
  */
-void displayText(char* line0, char* line1);
+void displayText(const char* line0, const char* line1);
 
 #endif /* DISPLAY_H_ */
diff --git a/lambda/lambda.c b/lambda/lambda.c
index 5cac9de..f5badd6 100644
--- a/lambda/lambda.c
+++ b/lambda/lambda.c
@@ -22,6 +22,7 @@
 #include <string.h>
 #include <avr/io.h>
 #include <avr/interrupt.h>
+#include <avr/pgmspace.h>
 #include "usart.h"
 #include "lcdroutines.h"
 #include "adc.h"
@@ -30,6 +31,8 @@
 #include "display.h"
 #include "alert.h"
 #include "command.h"
+#include "rules.h"
+#include "messages.h"
 
 /**
  * Does initialization, measures, displays and logs the measurements and
@@ -44,7 +47,7 @@
 	initInterrupts();
 	initTimers();
 
-	alert(1, 2, 31, "     Hello!     ", "");
+	alert_P(1, 2, 31, PSTR(MSG_WELCOME), PSTR(""));
 
 	Measurement meas;
 
@@ -56,6 +59,7 @@
 				logMeas(meas);
 			}
 			updateMeas(meas);
+			reason(meas);
 		}
 		if (isUSARTReceived()) {
 			char data[64];
diff --git a/lambda/messages.h b/lambda/messages.h
new file mode 100644
index 0000000..d11056d
--- /dev/null
+++ b/lambda/messages.h
@@ -0,0 +1,29 @@
+/*
+ * messages.h
+ *
+ *  Created on: 24.05.2015
+ *      Author: dode@luniks.net
+ */
+
+#ifndef MESSAGES_H_
+#define MESSAGES_H_
+
+/* lambda.c */
+#define MSG_WELCOME "     Hello!     "
+
+/* sensors.c */
+#define MSG_LEAN "Lean "
+#define MSG_OKAY "Okay "
+#define MSG_IDEAL "Ideal"
+#define MSG_RICH "Rich!"
+
+/* rules.c */
+#define MSG_AIRGATE_50_0 "Air gate 50%"
+#define MSG_AIRGATE_25_0 "Air gate 25%"
+#define MSG_AIRGATE_CLOSE_0 "Close air gate"
+#define MSG_AIRGATE_CLOSE_1 "Turn off heating"
+#define MSG_TOO_RICH_0 "Too rich, open"
+#define MSG_TOO_RICH_1 "air gate!"
+#define MSG_FIRE_OUT_0 "Fire out?"
+
+#endif /* MESSAGES_H_ */
diff --git a/lambda/rules.c b/lambda/rules.c
new file mode 100644
index 0000000..03b6956
--- /dev/null
+++ b/lambda/rules.c
@@ -0,0 +1,156 @@
+/*
+ * rules.c
+ *
+ *  Created on: 22.05.2015
+ *      Author: dode@luniks.net
+ */
+
+#include <avr/pgmspace.h>
+#include "alert.h"
+#include "integers.h"
+#include "rules.h"
+#include "messages.h"
+
+#define BEEPS 60
+#define LENGTH 20
+#define TONE 31
+
+#define DIR_NONE 0
+#define DIR_BURN_UP 1
+#define DIR_BURN_DOWN -1
+
+Measurement rulesMeasMax = {0, 0, 2000};
+Measurement rulesMeasPrev = {0, 0, 2000};
+uint16_t age = 0;
+int8_t dir = 0;
+
+/**
+ * Reminds to set the air gate to 50% when the fire is still building up
+ * and the temperature has reached 500°C.
+ */
+static void airgate50(bool* const fired, int8_t const dir,
+		Measurement const meas) {
+	if (! *fired && dir == DIR_BURN_UP && meas.tempI >= 500) {
+		alert_P(BEEPS, LENGTH, TONE, PSTR(MSG_AIRGATE_50_0), PSTR(""));
+		*fired = true;
+	}
+}
+
+/**
+ * Reminds to set the air gate to 25% when the fire is burning down and the
+ * temperature went below 800°C.
+ */
+static void airgate25(bool* const fired, int8_t const dir,
+		Measurement const meas) {
+	if (! *fired && dir == DIR_BURN_DOWN && meas.tempI < 800) {
+		alert_P(BEEPS, LENGTH, TONE, PSTR(MSG_AIRGATE_50_0), PSTR(""));
+		*fired = true;
+	}
+}
+
+/**
+ * Reminds to close the air gate when the fire is burning down and the
+ * temperature went below 400°C.
+ */
+static void airgateClose(bool* const fired, int8_t const dir,
+		Measurement const meas) {
+	if (! *fired && dir == DIR_BURN_DOWN && meas.tempI < 400) {
+		alert_P(BEEPS, LENGTH, TONE,
+				PSTR(MSG_AIRGATE_CLOSE_0), PSTR(MSG_AIRGATE_CLOSE_1));
+		*fired = true;
+	}
+}
+
+/**
+ * Notifies that the combustion is too rich and to open the air gate
+ * if possible.
+ */
+static void tooRich(bool* const fired, int8_t const dir,
+		Measurement const meas) {
+	if (! *fired && meas.tempI >= 100 && meas.lambda < 1200) {
+		alert_P(BEEPS, LENGTH, TONE,
+				PSTR(MSG_TOO_RICH_0), PSTR(MSG_TOO_RICH_1));
+		*fired = true;
+	}
+	if (meas.lambda >= 1300) {
+		*fired = false;
+	}
+}
+
+/**
+ * Notifies that the might have gone out at the beginning of building up.
+ */
+static void fireOut(bool* const fired, int8_t const dir,
+		Measurement const meas) {
+	if (! *fired && dir == DIR_BURN_UP && meas.tempI < 100 &&
+			meas.tempI < rulesMeasMax.tempI) {
+		alert_P(BEEPS, LENGTH, TONE, PSTR(MSG_FIRE_OUT_0), PSTR(""));
+		*fired = true;
+	}
+	if (meas.tempI >= 100) {
+		*fired = false;
+	}
+}
+
+/**
+ * Array of rules.
+ */
+Rule rules[] = {
+		{false, airgate50},
+		{false, airgate25},
+		{false, airgateClose},
+		{false, tooRich},
+		{false, fireOut}
+};
+
+// called about every second
+void reason(Measurement const meas) {
+
+	// apply the rules about every 10 seconds
+	if (age % 10 == 0) {
+		size_t rulesSize = sizeof(rules) / sizeof(rules[0]);
+		for (size_t i = 0; i < rulesSize; i++) {
+			rules[i].cond(&(rules[i].fired), dir, meas);
+		}
+	}
+
+	// try to figure out if the fire is building up or burning down by
+	// comparing current measurements with ones that are 3 minutes old.
+	if (age >= 180) {
+		dir = DIR_NONE;
+		if ((meas.tempI - rulesMeasPrev.tempI) >= 10 &&
+				rulesMeasMax.tempI < 800 && meas.lambda >= 2000) {
+			dir = DIR_BURN_UP;
+		} else if ((rulesMeasPrev.tempI - meas.tempI) >= 1 &&
+				rulesMeasMax.tempI > 800 && meas.lambda >= 2000) {
+			dir = DIR_BURN_DOWN;
+		}
+
+		rulesMeasPrev = meas;
+		age = 0;
+	}
+
+	rulesMeasMax.tempI = MAX(rulesMeasMax.tempI, meas.tempI);
+	rulesMeasMax.tempO = MAX(rulesMeasMax.tempO, meas.tempO);
+	rulesMeasMax.lambda = MIN(rulesMeasMax.lambda, meas.lambda);
+
+	age++;
+}
+
+void resetRules(void) {
+	rulesMeasPrev.tempI = 0;
+	rulesMeasPrev.tempO = 0;
+	rulesMeasPrev.lambda = 2000;
+
+	rulesMeasMax.tempI = 0;
+	rulesMeasMax.tempO = 0;
+	rulesMeasMax.lambda = 2000;
+
+	age = 0;
+	dir = DIR_NONE;
+
+	size_t rulesSize = sizeof(rules) / sizeof(rules[0]);
+	for (size_t i = 0; i < rulesSize; i++) {
+		rules[i].fired = false;
+	}
+}
diff --git a/lambda/rules.h b/lambda/rules.h
new file mode 100644
index 0000000..660deb5
--- /dev/null
+++ b/lambda/rules.h
@@ -0,0 +1,32 @@
+/*
+ * rules.h
+ *
+ *  Created on: 22.05.2015
+ *      Author: dode@luniks.net
+ */
+
+#ifndef RULES_H_
+#define RULES_H_
+
+#include <stdbool.h>
+#include "sensors.h"
+
+/**
+ * An attempt to create some sort of rule "object".
+ */
+typedef struct {
+	bool fired;
+	void (*cond)(bool* fired, int8_t dir, Measurement meas);
+} Rule;
+
+/**
+ * Applies all rules against the given measurements.
+ */
+void reason(Measurement meas);
+
+/**
+ * Resets all rules and internal state.
+ */
+void resetRules(void);
+
+#endif /* RULES_H_ */
diff --git a/lambda/sensors.c b/lambda/sensors.c
index 5b8fadf..fd4b18b 100644
--- a/lambda/sensors.c
+++ b/lambda/sensors.c
@@ -8,7 +8,6 @@
  *
  */
 
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <avr/io.h>
@@ -16,6 +15,7 @@
 #include "sensors.h"
 #include "integers.h"
 #include "pins.h"
+#include "messages.h"
 
 /**
  * Table used to look up the lambda value at 12 V heater voltage
@@ -146,12 +146,12 @@
 
 char* toInfo(uint16_t const lambda) {
 	if (lambda > 190) {
-		return LEAN;
+		return MSG_LEAN;
 	} else if (lambda > 150 && lambda <= 190) {
-		return OKAY;
+		return MSG_OKAY;
 	} else if (lambda >= 130 && lambda <= 150) {
-		return IDEAL;
+		return MSG_IDEAL;
 	} else {
-		return RICH;
+		return MSG_RICH;
 	}
 }
diff --git a/lambda/sensors.h b/lambda/sensors.h
index 3b13514..31f229b 100644
--- a/lambda/sensors.h
+++ b/lambda/sensors.h
@@ -11,11 +11,7 @@
 #ifndef SENSORS_H_
 #define SENSORS_H_
 
-// TODO put in Makefile?
-#define LEAN "Mager"
-#define OKAY "Okay "
-#define IDEAL "Ideal"
-#define RICH "Fett!"
+#include <stdio.h>
 
 /**
  * Entry for the lookup tables.
diff --git a/lambda/usart.c b/lambda/usart.c
index aaae4c5..0fee17c 100644
--- a/lambda/usart.c
+++ b/lambda/usart.c
@@ -53,9 +53,9 @@
 	if (size > 0) {
 	    data[0] = '\0';
 	    strncat(data, usartData, size - 1);
+	    memset(usartData, 0, sizeof(usartData));
+	    usartReceived = false;
 	}
-	memset(usartData, 0, sizeof(usartData));
-	usartReceived = false;
 }
 
 void printString(char* const data) {