diff --git a/app/Makefile b/app/Makefile
deleted file mode 100644
index 9af4b3e67..000000000
--- a/app/Makefile
+++ /dev/null
@@ -1,7 +0,0 @@
-app_objs += $(addprefix app/,\
-              escher_demo.o\
-              plot.o\
-              utils.o)
-products += $(app_objs) app.elf app.hex app.bin
-
-app.elf: $(app_objs)
diff --git a/app/app.cpp b/app/app.cpp
deleted file mode 100644
index 1cc599cc8..000000000
--- a/app/app.cpp
+++ /dev/null
@@ -1,179 +0,0 @@
-extern "C" {
-#include <assert.h>
-#include <kandinsky.h>
-#include <stdlib.h>
-#include <ion.h>
-}
-
-#include <poincare.h>
-#include "../poincare/src/layout/string_layout.h"
-
-#include "plot.h"
-#include "utils.h"
-
-static const char* kParsingErrorMessage = "PARSING ERROR";
-
-//////////////////////////////////////////////////////
-
-static constexpr uint8_t kInputMemory = 15;
-
-typedef struct user_expression_t {
-  char* text_input;
-  Expression* expression;
-  Expression* simplified;
-  ExpressionLayout* expression_layout;
-  ExpressionLayout* simplified_layout;
-} user_expression_t;
-
-class UserExpressions {
-  public:
-    UserExpressions() {
-      m_numberOfExpressions = 0;
-      m_position = kInputMemory;
-      for (int i=0; i<kInputMemory; i++) {
-        m_expressions[i] = {nullptr, nullptr, nullptr, nullptr, nullptr};
-      }
-    }
-
-    // Adds a user expression as the most recent one.
-    void append_expression(user_expression_t user_expression) {
-      if (m_numberOfExpressions < kInputMemory) {
-        m_numberOfExpressions++;
-      }
-      m_position = (m_position + 1) % kInputMemory;
-      if (m_position < 0) {
-        m_numberOfExpressions += kInputMemory;
-      }
-
-      // The circular buffer is full, now we have to erase stuff.
-      if (m_numberOfExpressions == kInputMemory) {
-        user_expression_t tmp = m_expressions[m_position];
-        if (tmp.text_input) {
-          free(tmp.text_input);
-          if (tmp.expression) {
-            free(tmp.expression);
-            if (tmp.expression_layout) {
-              free(tmp.expression_layout);
-            }
-            if (tmp.simplified && tmp.simplified != tmp.expression) {
-              free(tmp.simplified);
-              if (tmp.simplified_layout) {
-                free(tmp.simplified_layout);
-              }
-            }
-          }
-        }
-      }
-      m_expressions[m_position] = user_expression;
-    }
-
-    // Gets the i th latest expression.
-    user_expression_t get_expression(uint8_t index) const {
-      //assert(index < m_numberOfExpressions);
-      int pos = (m_position - index) % kInputMemory;
-      if (pos < 0) {
-        pos += kInputMemory;
-      }
-      return m_expressions[pos];
-    }
-
-    uint8_t numberOfExpressions() const {
-      return m_numberOfExpressions;
-    }
-
-  private:
-    uint8_t m_numberOfExpressions;
-    uint8_t m_position;
-    user_expression_t m_expressions[kInputMemory];
-};
-
-/////////////////////////////////////////////////
-
-static user_expression_t create_user_input(char* text) {
-  user_expression_t user_expression = {text, nullptr, nullptr, nullptr, nullptr};
-  user_expression.expression = Expression::parse(user_expression.text_input);
-  if (user_expression.expression) {
-    user_expression.expression_layout = user_expression.expression->createLayout();
-    user_expression.simplified = user_expression.expression->simplify();
-    user_expression.simplified_layout = user_expression.simplified->createLayout();
-  } else {
-    user_expression.expression_layout =
-      new StringLayout(kParsingErrorMessage, strlen(kParsingErrorMessage));
-  }
-  return user_expression;
-}
-
-static int16_t print_user_input(user_expression_t user_expression, int16_t yOffset) {
-  if (user_expression.expression_layout) {
-    int16_t height = user_expression.expression_layout->size().height;
-    if (yOffset + height < ION_SCREEN_HEIGHT) {
-      user_expression.expression_layout->draw(KDPointMake(0, yOffset));
-    }
-    yOffset += height;
-  }
-  if (user_expression.simplified_layout) {
-    int16_t height = user_expression.simplified_layout->size().height;
-    if (yOffset + height < ION_SCREEN_HEIGHT) {
-      int16_t xOffset = ION_SCREEN_WIDTH - user_expression.simplified_layout->size().width;
-      user_expression.simplified_layout->draw(KDPointMake(xOffset, yOffset));
-    }
-    yOffset += height;
-  }
-  return yOffset;
-}
-
-static void print_user_inputs(const UserExpressions& user_inputs, uint8_t startingAt) {
-  int16_t yOffset = 0;
-  for (uint8_t i=startingAt; i<user_inputs.numberOfExpressions(); i++) {
-    yOffset = print_user_input(user_inputs.get_expression(i), yOffset);
-    if (yOffset>ION_SCREEN_HEIGHT) {
-      break;
-    }
-  }
-}
-
-static void interactive_expression_parsing() {
-  UserExpressions user_inputs = UserExpressions();
-  int index = 0;
-  while (1) {
-    text_event_t text_event;
-    if (index == 0) {
-      text_event = get_text(nullptr);
-    } else {
-      text_event = get_text(user_inputs.get_expression(index - 1).text_input);
-    }
-    if (text_event.event == EQUAL) {
-      user_inputs.append_expression(create_user_input(text_event.text));
-    } else if (text_event.event == UP_ARROW) {
-      index--;
-      if (index < 0) {
-        index = 0;
-      }
-    } else if (text_event.event == DOWN_ARROW) {
-      if (user_inputs.numberOfExpressions() != 0) {
-        index++;
-        if (index >= user_inputs.numberOfExpressions()) {
-          index = user_inputs.numberOfExpressions() - 1;
-        }
-      }
-    } else if (text_event.event == PLOT) {
-      user_inputs.append_expression(create_user_input(text_event.text));
-      // We check that the expression is correct.
-      if (user_inputs.get_expression(0).expression) {
-        clear_screen();
-        plot(user_inputs.get_expression(0).expression, -3, 3);
-      }
-    } else {
-      assert(false); // unreachable.
-    }
-    clear_screen();
-    print_user_inputs(user_inputs, index ? index - 1 : 0);
-  }
-}
-
-void ion_app() {
-  interactive_expression_parsing();
-  while (1) {
-    ion_sleep();
-  }
-}
diff --git a/app/blinky.c b/app/blinky.c
deleted file mode 100644
index 379bd52a7..000000000
--- a/app/blinky.c
+++ /dev/null
@@ -1,44 +0,0 @@
-#include <registers.h>
-
-void sleep(long delay);
-
-int main(int argc, char * argv[]) {
-
-  // We want to blink LEDs connected to GPIO pin G13 and G14
-  // (this is documented in our board's PDF)
-  //
-  // GPIO are grouped by letter, and GPIO "G" live on the "AHB1" bus
-  // (this is documented in the STM32F4 reference mnual, page 65)
-
-  // Step 1 : Enable clock in RCC_AHBxENR
-  RCC_AHB1ENR->GPIOGEN = 1;
-
-
-  // Step 2 : Configure the GPIO pin to "general purpose output
-  GPIO_MODER(GPIOG)->MODER13 = GPIO_MODE_OUTPUT;
-  GPIO_MODER(GPIOG)->MODER14 = GPIO_MODE_OUTPUT;
-
-  // Per doc, the output is push-pull by default (yay)
-  // And we should also set the output speed, but really
-  // we don't care (we're doing something super slow)
-
-  long delay = 50000;
-
-  while (1) {
-    GPIO_ODR(GPIOG)->ODR13 = 0;
-    GPIO_ODR(GPIOG)->ODR14 = 1;
-
-    sleep(delay);
-
-    GPIO_ODR(GPIOG)->ODR13 = 1;
-    GPIO_ODR(GPIOG)->ODR14 = 0;
-
-    sleep(delay);
-  }
-}
-
-void sleep(long delay) {
-  for (long i=0; i<delay; i++) {
-    // Do nothing!
-  }
-}
diff --git a/app/freertos_blinky.c b/app/freertos_blinky.c
deleted file mode 100644
index 40ba72caa..000000000
--- a/app/freertos_blinky.c
+++ /dev/null
@@ -1,57 +0,0 @@
-#include <registers.h>
-#include <FreeRTOS.h>
-#include <task.h>
-#include <timers.h>
-#include <semphr.h>
-
-void BlinkGreenLed(void * pvParameters) {
-  while(1) {
-    vTaskDelay(1000/portTICK_PERIOD_MS);
-    GPIO_ODR(GPIOG)->ODR13 = 0;
-    vTaskDelay(1000/portTICK_PERIOD_MS);
-    GPIO_ODR(GPIOG)->ODR13 = 1;
-  }
-}
-
-void BlinkRedLed(void * pvParameters) {
-  int delay = 10;
-  while (1) {
-    vTaskDelay(delay);
-    GPIO_ODR(GPIOG)->ODR14 = 1;
-    vTaskDelay(delay);
-    GPIO_ODR(GPIOG)->ODR14 = 0;
-    delay++;
-  }
-}
-
-int main(int argc, char * argv[]) {
-    // We want to blink LEDs connected to GPIO pin G13 and G14
-  // (this is documented in our board's PDF)
-  //
-  // GPIO are grouped by letter, and GPIO "G" live on the "AHB1" bus
-  // (this is documented in the STM32F4 reference mnual, page 65)
-
-  // Step 1 : Enable clock in RCC_AHBxENR
-  RCC_AHB1ENR->GPIOGEN = 1;
-
-
-  // Step 2 : Configure the GPIO pin to "general purpose output
-  GPIO_MODER(GPIOG)->MODER13 = GPIO_MODE_OUTPUT;
-  GPIO_MODER(GPIOG)->MODER14 = GPIO_MODE_OUTPUT;
-
-
-  BaseType_t success = xTaskCreate(BlinkGreenLed,
-      "BlkGrn",
-      100, // Stack size
-      NULL, // Parameters
-      2,
-      NULL);
-
-  xTaskCreate(BlinkRedLed, "BlkRed", 100, NULL, 2, NULL);
-
-  vTaskStartScheduler();
-
-  while (1) {
-    // We should never get here
-  }
-}
diff --git a/app/plot.cpp b/app/plot.cpp
deleted file mode 100644
index bef6bbce0..000000000
--- a/app/plot.cpp
+++ /dev/null
@@ -1,85 +0,0 @@
-extern "C" {
-#include <assert.h>
-#include <kandinsky.h>
-#include <stdlib.h>
-#include <ion.h>
-}
-
-#include <poincare.h>
-
-#include "utils.h"
-#include "plot.h"
-
-constexpr KDCoordinate kScreenWidth = ION_SCREEN_WIDTH;
-const KDCoordinate kScreenHeight = ION_SCREEN_HEIGHT;
-
-static float plotValues[kScreenWidth];
-static float yMin, yMax;
-
-// For now we only plot the axes at the origin.
-// TODO: print axes not at the origin with some values too.
-// TODO: label the axes.
-// TODO: put the values on the axes.
-static void plot_axes(float xMin, float xMax, float yMin, float yMax) {
-  if (xMin < 0 && xMax > 0) {
-    float total = xMax - xMin;
-    float ratio = xMax / total;
-    KDCoordinate width = ratio * kScreenWidth;
-    KDDrawLine(KDPointMake(width, 0), KDPointMake(width, kScreenHeight-1), 0xff);
-  }
-  if (yMin < 0 && yMax > 0) {
-    float total = yMax - yMin;
-    float ratio = yMax / total;
-    KDCoordinate height = ratio * kScreenHeight;
-    KDDrawLine(KDPointMake(0, height), KDPointMake(kScreenWidth-1, height), 0xff);
-  }
-}
-
-static void fill_values(Expression * e, float xMin, float xMax) {
-  assert(e);
-  Context plotContext;
-
-  // Initialize min and max.
-  Float xExp = Float(xMin);
-  plotContext.setExpressionForSymbolName(&xExp, "x");
-  plotValues[0] = e->approximate(plotContext);
-  yMin = plotValues[0];
-  yMax = plotValues[0];
-
-  for (KDCoordinate i = 1; i < kScreenWidth; i++) {
-    float x = xMin + (xMax-xMin)/kScreenWidth*i;
-    Float xExp = Float(x);
-    plotContext.setExpressionForSymbolName(&xExp, "x");
-    plotValues[i] = e->approximate(plotContext);
-    if (plotValues[i] > yMax) {
-      yMax = plotValues[i];
-    }
-    if (plotValues[i] < yMin) {
-      yMin = plotValues[i];
-    }
-  }
-}
-
-// TODO: Add a cursor.
-// TODO: print the expression.
-void plot(Expression * e, float xMin, float xMax) {
-  assert(e);
-
-  fill_values(e, xMin, xMax);
-
-  // Plot the original axes.
-  plot_axes(xMin, xMax, yMin, yMax);
-
-  // We need to initialize the first point.
-  KDCoordinate j = ((plotValues[0]-yMin) / (yMax-yMin) * (kScreenHeight - 1));
-  KDPoint previousPoint = KDPointMake(0, kScreenHeight - 1 - j);
-
-  for (KDCoordinate i = 1; i < kScreenWidth; i++) {
-    // TODO: check for yMin == yMax
-    KDCoordinate j = ((plotValues[i]-yMin) / (yMax-yMin) * (kScreenHeight - 1));
-    KDPoint currentPoint = KDPointMake(i, kScreenHeight - 1 - j);
-    KDDrawLine(previousPoint, currentPoint, 0xFF);
-    previousPoint = currentPoint;
-  }
-  ion_get_event(); // We wait for a text input.
-}
diff --git a/app/plot.h b/app/plot.h
deleted file mode 100644
index e66f97bdd..000000000
--- a/app/plot.h
+++ /dev/null
@@ -1,7 +0,0 @@
-#ifndef APP_PLOT_H
-#define APP_PLOT_H
-
-// Note that currently the only variable is 'x'
-void plot(Expression * e, float xMin, float xMax);
-
-#endif
diff --git a/app/spi.c b/app/spi.c
deleted file mode 100644
index db8aa735d..000000000
--- a/app/spi.c
+++ /dev/null
@@ -1,79 +0,0 @@
-#include <registers.h>
-#include <FreeRTOS.h>
-#include <task.h>
-#include <timers.h>
-#include <semphr.h>
-
-/* This code sends data over SPI
- * We're using SPI4, in this pinout
- *
- * PE11 - SPI4_NSS - Yellow
- * PE12 - SPI4_SCK - Green
- * PE13 - SPI4_MISO - Red
- * PE14 - SPI4_MOSI - Blue
- */
-
-void SpiSend(void * pvParameters) {
-  uint16_t value = 0;
-  while(1) {
-    SPI_SR_t * spi_status = SPI_SR(SPI4);
-    if (spi_status->BSY == 0) {
-      uint16_t * SPI4_DR = (uint16_t *)(0x4001340C);
-      *SPI4_DR = value++;
-    }
-    vTaskDelay(100/portTICK_PERIOD_MS);
-  }
-}
-
-int main(int argc, char * argv[]) {
-  // We'll use GPIO pins E11-E14 to emit SPI data
-  // GPIO are grouped by letter, and GPIO "G" live on the "AHB1" bus (as all GPIOs BTW)
-  // (this is documented in the STM32F4 reference mnual, page 65)
-
-  // Step 1 : Enable clock in RCC_AHBxENR
-  RCC_AHB1ENR->GPIOEEN = 1;
-
-  // Step 2 : Configure the GPIO pin to "Alternate function number 5"
-  // This means "SPI4 on pins E11-14", cf STM32F249 p78
-  GPIO_MODER(GPIOE)->MODER11 = GPIO_MODE_ALTERNATE_FUNCTION;
-  GPIO_MODER(GPIOE)->MODER12 = GPIO_MODE_ALTERNATE_FUNCTION;
-  GPIO_MODER(GPIOE)->MODER13 = GPIO_MODE_ALTERNATE_FUNCTION;
-  GPIO_MODER(GPIOE)->MODER14 = GPIO_MODE_ALTERNATE_FUNCTION;
-
-  // We're interested in pins 11-14, which are in the 8-16 range, so we
-  // have to deal with the "high" version of the AF register
-  GPIO_AFRH(GPIOE)->AFRH11 = GPIO_AF_AF5;
-  GPIO_AFRH(GPIOE)->AFRH12 = GPIO_AF_AF5;
-  GPIO_AFRH(GPIOE)->AFRH13 = GPIO_AF_AF5;
-  GPIO_AFRH(GPIOE)->AFRH14 = GPIO_AF_AF5;
-
-  // Enable the SPI4 clock
-  RCC_APB2ENR->SPI4EN = 1;
-
-  // Configure the SPI port
-  // Using a C99 compound litteral
-  *SPI_CR1(SPI4) = (SPI_CR1_t){
-    .BIDIMODE = 1,
-    .BIDIOE = 1,
-    .MSTR = 1,
-    .DFF = SPI_DFF_16_BITS,
-    .CPOL = 0,
-    .BR = SPI_BR_DIV_256,
-    .SSM = 1,
-    .SSI = 1,
-    .SPE = 1
-  };
-
-  BaseType_t success = xTaskCreate(SpiSend,
-      "SpiSnd",
-      100, // Stack size
-      NULL, // Parameters
-      2,
-      NULL);
-
-  vTaskStartScheduler();
-
-  while (1) {
-    // We should never get here
-  }
-}
diff --git a/app/utils.cpp b/app/utils.cpp
deleted file mode 100644
index db8ab9df2..000000000
--- a/app/utils.cpp
+++ /dev/null
@@ -1,195 +0,0 @@
-extern "C" {
-#include <assert.h>
-#include <kandinsky.h>
-#include <stdlib.h>
-#include <string.h>
-}
-
-#include "utils.h"
-
-static constexpr int16_t kPromptHeight = 25;
-static constexpr uint8_t kBufferSize = 255;
-
-void clear_screen() {
-  KDRect r;
-  r.x = 0;
-  r.y = 0;
-  r.width = ION_SCREEN_WIDTH;
-  r.height = ION_SCREEN_HEIGHT;
-  KDFillRect(r, 0x00);
-}
-
-static void clear_prompt() {
-  KDRect r;
-  r.x = 0;
-  r.y = ION_SCREEN_HEIGHT - kPromptHeight;
-  r.width = ION_SCREEN_WIDTH;
-  r.height = kPromptHeight;
-  KDFillRect(r, 0x00);
-}
-
-static void print_prompt(char* text, int index) {
-  char* tmp = (char*) " ";
-  KDSize font_size = KDStringSize(tmp);
-  KDDrawLine(KDPointMake(0, ION_SCREEN_HEIGHT - kPromptHeight),
-             KDPointMake(ION_SCREEN_WIDTH, ION_SCREEN_HEIGHT - kPromptHeight), 0xff);
-  KDDrawString(text, KDPointMake(0, ION_SCREEN_HEIGHT - (kPromptHeight / 2)), 0);
-  KDDrawChar(text[index], KDPointMake(index * font_size.width, ION_SCREEN_HEIGHT - (kPromptHeight / 2)), true);
-}
-
-static void clear_trig_menu() {
-  {
-    KDRect r;
-    r.x = ION_SCREEN_WIDTH / 4 - 1;
-    r.y = ION_SCREEN_HEIGHT / 4 - 1;
-    r.width = ION_SCREEN_WIDTH / 2 + 2;
-    r.height = ION_SCREEN_HEIGHT / 2 + 2;
-    KDFillRect(r, 0x00);
-  }
-}
-
-static void print_trig_menu() {
-  {
-    KDRect r;
-    r.x = ION_SCREEN_WIDTH / 4;
-    r.y = ION_SCREEN_HEIGHT / 4;
-    r.width = ION_SCREEN_WIDTH / 2;
-    r.height = ION_SCREEN_HEIGHT / 2;
-    KDDrawRect(r, 0xff);
-  }
-}
-
-static int get_trig_input(char* input) {
-  int pos = 0;
-  const char* kTexts[] = {
-    "sine",
-    "cosine",
-    "tangent",
-    "cancel"
-  };
-  const char* kOutputs[] = {
-    "sin( )",
-    "cos( )",
-    "tan( )",
-  };
-  const KDPoint orig = KDPointMake(ION_SCREEN_WIDTH / 4, ION_SCREEN_HEIGHT / 4);
-  while (true) {
-    print_trig_menu();
-
-    uint16_t vert_acc = 0;
-    for (int i(0); i<4; i++) {
-      KDSize text_size = KDStringSize(kTexts[i]);
-      KDDrawString(kTexts[i],
-          KDPointMake(orig.x, orig.y + vert_acc + text_size.height / 2),
-          i==pos);
-      vert_acc += text_size.height;
-    }
-
-    ion_event_t event = ion_get_event();
-    if (event == UP_ARROW) {
-      pos--;
-      if (pos < 0) {
-        pos = 0;
-      }
-    } else if (event == DOWN_ARROW) {
-      pos++;
-      if (pos >= 4) {
-        pos = 3;
-      }
-    } else if (event == '=') {
-      clear_trig_menu();
-      if (pos == 3) {
-        return 0;
-      } else {
-        memcpy(input, kOutputs[pos], (size_t) strlen(kOutputs[pos]));
-        return strlen(kOutputs[pos]);
-      }
-    }
-  }
-}
-
-text_event_t get_text(char* txt) {
-  char input[kBufferSize];
-  int index = 0;
-  int max = 0;
-  text_event_t text_event = {nullptr, ERROR};
-
-  for (int i = 0; i < kBufferSize; i++) {
-    input[i] = 0;
-  }
-
-  if (txt != nullptr) {
-    index = strlen(txt);
-    max = index;
-    memcpy(input, txt, (size_t) index);
-  }
-
-  input[max] = ' ';
-  input[max+1] = '\0';
-
-  while (1) {
-    clear_prompt();
-    print_prompt(input, index);
-    ion_event_t event = ion_get_event();
-    if (event == EQUAL) {
-      input[max] = '\0';
-      text_event.event = EQUAL;
-      text_event.text = (char*) malloc(sizeof(char) * (index + 1));
-      memcpy(text_event.text, input, (size_t) (index + 1));
-      break;
-    } else if (event == LEFT_ARROW) {
-      index--;
-      if (index < 0) {
-        index = 0;
-      }
-    } else if (event == RIGHT_ARROW) {
-        if (index < max) {
-          index++;
-        }
-    } else if (event <= 0x7f) {
-      input[index++] = (char) event;
-      // We are at the end of the line.
-      if (index > max) {
-        max=index;
-        input[max] = ' ';
-        input[max+1] = '\0';
-      }
-    } else if (event == TRIG_MENU) {
-      int tmp = get_trig_input(&input[index]);
-      index+=tmp;
-      if (index > max) {
-        max=index;
-        input[max] = ' ';
-        input[max+1] = '\0';
-      }
-      // we want to be inside the parenthese if there are some.
-      index -= (tmp > 2) ? 2 : 0;
-    } else if (event == DELETE) {
-      // Nothing to delete.
-      if (index == max) {
-        continue;
-      }
-      for (int i=index; i<max+1; i++) {
-        input[i] = input[i+1];
-      }
-      max--;
-    } else if (event == UP_ARROW) {
-      text_event.event = UP_ARROW;
-      break;
-    } else if (event == DOWN_ARROW) {
-      text_event.event = DOWN_ARROW;
-      break;
-    } else if (event == PLOT) {
-      text_event.event = PLOT;
-      input[max] = '\0';
-      text_event.text = (char*) malloc(sizeof(char) * (index + 1));
-      memcpy(text_event.text, input, (size_t) (index + 1));
-      break;
-    } else {
-      assert(false); // unreachable.
-    }
-  }
-
-  clear_prompt();
-  return text_event;
-}
diff --git a/app/utils.h b/app/utils.h
deleted file mode 100644
index bc48f0b8d..000000000
--- a/app/utils.h
+++ /dev/null
@@ -1,22 +0,0 @@
-#ifndef APP_UTILS_H
-#define APP_UTILS_H
-
-extern "C" {
-#include <ion.h>
-}
-
-typedef struct {
-  char* text;
-  ion_event_t event;
-} text_event_t;
-
-/* Returns a pointer to an input text allocated by the functions.
- * Also returns an event, which is its return reason.
- *
- * This function can get a text to work on instead of starting from an empty
- * string. */
-text_event_t get_text(char* txt);
-
-void clear_screen();
-
-#endif // APP_UTILS_H