diff --git a/surveys/code_coverage/.gitignore b/surveys/code_coverage/.gitignore
new file mode 100644
index 0000000..404abb2
--- /dev/null
+++ b/surveys/code_coverage/.gitignore
@@ -0,0 +1 @@
+coverage/
diff --git a/surveys/code_coverage/README.md b/surveys/code_coverage/README.md
new file mode 100644
index 0000000..12edb8d
--- /dev/null
+++ b/surveys/code_coverage/README.md
@@ -0,0 +1,20 @@
+# Code coverage survery
+
+## Test
+
+```
+deno task test-coverage
+```
+
+## Instructions
+
+Write 1) a test inside `program_1_test.ts`, testing `playerFromUnknown` and 2) a test inside `program_2_test.ts`, testing `stringToInt`. The goal should be to __test as much as the code as possible__, meaning every branch and every line of code should be tested.
+
+The tests are done, when the participant is satisfied (or the time is up). Afterward, generate a coverage report using the following command.
+
+```sh
+deno task test-coverage
+```
+
+Note down the branch and line coverage percentages of each file.
+
diff --git a/surveys/code_coverage/deno.jsonc b/surveys/code_coverage/deno.jsonc
new file mode 100644
index 0000000..7aac543
--- /dev/null
+++ b/surveys/code_coverage/deno.jsonc
@@ -0,0 +1,8 @@
+{
+    "fmt": {
+        "indentWidth": 4
+    },
+    "tasks": {
+        "test-coverage": "deno test --coverage && deno coverage coverage/ && deno coverage coverage/ --html && firefox --file coverage/html/index.html"
+    }
+}
diff --git a/surveys/code_coverage/deno.lock b/surveys/code_coverage/deno.lock
new file mode 100644
index 0000000..b742530
--- /dev/null
+++ b/surveys/code_coverage/deno.lock
@@ -0,0 +1,18 @@
+{
+  "version": "4",
+  "specifiers": {
+    "jsr:@std/assert@*": "1.0.8",
+    "jsr:@std/internal@^1.0.5": "1.0.5"
+  },
+  "jsr": {
+    "@std/assert@1.0.8": {
+      "integrity": "ebe0bd7eb488ee39686f77003992f389a06c3da1bbd8022184804852b2fa641b",
+      "dependencies": [
+        "jsr:@std/internal"
+      ]
+    },
+    "@std/internal@1.0.5": {
+      "integrity": "54a546004f769c1ac9e025abd15a76b6671ddc9687e2313b67376125650dc7ba"
+    }
+  }
+}
diff --git a/surveys/code_coverage/program_1.ts b/surveys/code_coverage/program_1.ts
new file mode 100644
index 0000000..97d21ae
--- /dev/null
+++ b/surveys/code_coverage/program_1.ts
@@ -0,0 +1,50 @@
+export type Player = {
+    username: string;
+    level: number;
+};
+
+export type Result<T> = { ok: true; value: T } | { ok: false; error: string };
+
+export function playerFromUnknown(input: unknown): Result<Player> {
+    if (input === undefined) {
+        return { ok: false, error: "no input" };
+    }
+    if (input === null) {
+        return { ok: false, error: "no input" };
+    }
+    if (typeof input === "string") {
+        if (!/^[\d\w(:?\\\-)]+\-\d+$/.test(input)) {
+            return { ok: false, error: "malformed player" };
+        }
+        const splits = input.split("-");
+        let username = splits[0];
+        if (username.includes("\\-")) {
+            username = username.replaceAll("\\-", "-");
+        }
+        if (splits[1].startsWith("0") && splits[1].length >= 2) {
+            return { ok: false, error: "malformed player" };
+        }
+        const level = parseInt(splits[1]);
+        return { ok: true, value: { username, level } };
+    } else if (typeof input === "object") {
+        if (Object.keys(input).length < 2) {
+            return { ok: false, error: "malformed player" };
+        }
+        if (Object.keys(input).length > 2) {
+            return { ok: false, error: "too much information" };
+        }
+        if (!("username" in input && "level" in input)) {
+            return { ok: false, error: "malformed player" };
+        }
+        if (typeof input.username !== "string") {
+            return { ok: false, error: "malformed player" };
+        }
+        if (typeof input.level !== "number") {
+            return { ok: false, error: "malformed player" };
+        }
+        const { username, level } = input;
+        return { ok: true, value: { username, level } };
+    } else {
+        return { ok: false, error: "malformed player" };
+    }
+}
diff --git a/surveys/code_coverage/program_1_test.ts b/surveys/code_coverage/program_1_test.ts
new file mode 100644
index 0000000..a15bc89
--- /dev/null
+++ b/surveys/code_coverage/program_1_test.ts
@@ -0,0 +1,13 @@
+import { assertEquals } from "jsr:@std/assert";
+import { playerFromUnknown } from "./program_1.ts";
+
+Deno.test("must work", () => {
+    assertEquals(
+        playerFromUnknown("miklz-33"),
+        { ok: true, value: { username: "miklz", level: 33 } },
+    );
+    assertEquals(
+        playerFromUnknown({ username: "piet", level: 2 }),
+        { ok: true, value: { username: "piet", level: 2 } },
+    );
+});
diff --git a/surveys/code_coverage/program_2.ts b/surveys/code_coverage/program_2.ts
new file mode 100644
index 0000000..65c7edd
--- /dev/null
+++ b/surveys/code_coverage/program_2.ts
@@ -0,0 +1,45 @@
+// deno-fmt-ignore
+const charVal: {[key: string]: number} = {
+    "0": 0, "1": 1, "2": 2, "3": 3,
+    "4": 4, "5": 5, "6": 6, "7": 7,
+    "8": 8, "9": 9, "a": 10, "b": 11,
+    "c": 12, "d": 13, "e": 14, "f": 15,
+};
+const base2Digits = ["0", "1"];
+const base8Digits = [...base2Digits, "2", "3", "4", "5", "6", "7"];
+const base10Digits = [...base8Digits, "8", "9"];
+const base16Digits = [...base10Digits, "a", "b", "c", "d", "e", "f"];
+
+export function stringToInt(text: string): number {
+    if (text.length === 0) {
+        return NaN;
+    }
+    if (text[0] === "0") {
+        if (text.length === 1) {
+            return 0;
+        } else if (text[1] == "b") {
+            return parseDigits(text.slice(2), 2, base2Digits);
+        } else if (text[1] == "x") {
+            return parseDigits(text.slice(2), 16, base16Digits);
+        } else {
+            return parseDigits(text.slice(1), 8, base8Digits);
+        }
+    }
+    return parseDigits(text, 10, base10Digits);
+}
+
+function parseDigits(
+    numberText: string,
+    base: number,
+    digitSet: string[],
+): number {
+    let value = 0;
+    for (const ch of numberText) {
+        value *= base;
+        if (!digitSet.includes(ch)) {
+            return NaN;
+        }
+        value += charVal[ch];
+    }
+    return value;
+}
diff --git a/surveys/code_coverage/program_2_test.ts b/surveys/code_coverage/program_2_test.ts
new file mode 100644
index 0000000..e0425e2
--- /dev/null
+++ b/surveys/code_coverage/program_2_test.ts
@@ -0,0 +1,11 @@
+import { assertEquals } from "jsr:@std/assert";
+import { stringToInt } from "./program_2.ts";
+
+Deno.test("must work", () => {
+    assertEquals(stringToInt("0"), 0);
+    assertEquals(stringToInt("10"), 10);
+    assertEquals(stringToInt("0b110"), 6);
+    assertEquals(stringToInt("071"), 57);
+    assertEquals(stringToInt("0xaa"), 170);
+    assertEquals(stringToInt("john"), NaN);
+});
diff --git a/surveys/code_coverage/survey.ods b/surveys/code_coverage/survey.ods
new file mode 100644
index 0000000..e5da3de
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diff --git a/surveys/flame_graph/README.md b/surveys/flame_graph/README.md
new file mode 100644
index 0000000..c3243b2
--- /dev/null
+++ b/surveys/flame_graph/README.md
@@ -0,0 +1,38 @@
+
+# Flame graph survey
+
+Look at the following code.
+
+```rs
+fn add(a, b) {
+    + a b
+}
+
+let result = 0;
+let i = 0;
+loop {
+    if >= i 10 {
+        break;
+    }
+    result = add(result, 5);
+    i = + i 1;
+}
+```
+
+Imagine you were to run the code.
+```
+slige --run program.slg
+```
+
+What percantage distribution of the total execution time is spent in `main` and in `add`? Remember that all time spent in `add` is also time spent in `main`.
+
+Examples:
+
+Total program | Inside `main` | Inside `add`
+---|---|---
+100% | 80% | 40%
+100% | 90% | 10%
+100% | 96% | 70%
+
+Note down the guesses.
+
diff --git a/surveys/flame_graph/program_flame_graph.png b/surveys/flame_graph/program_flame_graph.png
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diff --git a/surveys/flame_graph/survey.ods b/surveys/flame_graph/survey.ods
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index 0000000..72153e3
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diff --git a/web/example.slg b/web/example.slg
new file mode 100644
index 0000000..927726f
--- /dev/null
+++ b/web/example.slg
@@ -0,0 +1,14 @@
+fn add(a, b) {
+    + a b
+}
+
+let result = 0;
+let i = 0;
+loop {
+    if >= i 10 {
+        break;
+    }
+    result = add(result, 5);
+    i = + i 1;
+}
+