diff --git a/README.md b/README.md
index 798c433..465eb89 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,3 @@
 # AoC Lib
 
-This is a semi-private collection of helpers to solve [Advent of code](http://adventofcode.com) puzzles.
+This is a semi-private collection of helpers to solve [Advent of code](https://adventofcode.com) puzzles.
diff --git a/lib/src/main/kotlin/de/linkel/aoc/utils/IntRangeMixIn.kt b/lib/src/main/kotlin/de/linkel/aoc/utils/IntRangeMixIn.kt
new file mode 100644
index 0000000..86e71bc
--- /dev/null
+++ b/lib/src/main/kotlin/de/linkel/aoc/utils/IntRangeMixIn.kt
@@ -0,0 +1,9 @@
+package de.linkel.aoc.utils
+
+fun IntRange.intersects(other: IntRange): Boolean {
+    return (this.first <= other.first && this.last >= other.first) || (other.first <= this.first && other.last >= this.first)
+}
+
+fun IntRange.extend(front: Int = 0, back: Int = 0): IntRange {
+    return IntRange(this.first - front, this.last + back)
+}
diff --git a/lib/src/main/kotlin/de/linkel/aoc/utils/SequenceMixIn.kt b/lib/src/main/kotlin/de/linkel/aoc/utils/SequenceMixIn.kt
new file mode 100644
index 0000000..571a315
--- /dev/null
+++ b/lib/src/main/kotlin/de/linkel/aoc/utils/SequenceMixIn.kt
@@ -0,0 +1,68 @@
+package de.linkel.aoc.utils
+
+fun <T> Sequence<T>.prepend(element: T): Sequence<T> {
+    return if (this is ConcatSequence<T>) {
+        ConcatSequence(listOf(sequenceOf(element)) + this.sequences)
+    } else {
+        ConcatSequence(listOf(sequenceOf(element), this))
+    }
+}
+fun <T> Sequence<T>.prepend(other: Sequence<T>): Sequence<T> {
+    return if (this is ConcatSequence<T>) {
+        ConcatSequence(listOf(other) + this.sequences)
+    } else {
+        ConcatSequence(listOf(other, this))
+    }
+}
+fun <T> Sequence<T>.append(element: T): Sequence<T> {
+    return if (this is ConcatSequence<T>) {
+        ConcatSequence(this.sequences + listOf(sequenceOf(element)))
+    } else {
+        ConcatSequence(listOf(this, sequenceOf(element)))
+    }
+}
+fun <T> Sequence<T>.append(other: Sequence<T>): Sequence<T> {
+    return if (this is ConcatSequence<T>) {
+        ConcatSequence(this.sequences + listOf(other))
+    } else {
+        ConcatSequence(listOf(this, other))
+    }
+}
+operator fun <T> Sequence<T>.plus(other: Sequence<T>): Sequence<T> {
+    return if (this is ConcatSequence<T>) {
+        ConcatSequence(this.sequences + listOf(other))
+    } else {
+        ConcatSequence(listOf(this, other))
+    }
+}
+
+class ConcatSequence<T>(
+    val sequences: List<Sequence<T>>
+): Sequence<T> {
+    override fun iterator(): Iterator<T> {
+        return ConcatIterator(sequences.map { it.iterator() })
+    }
+}
+
+class ConcatIterator<T>(
+    iterators: List<Iterator<T>>
+): Iterator<T> {
+    private val parents = iterators.toMutableList()
+    private var current: Iterator<T>? = null
+
+    private fun cycleIfNecessary() {
+        while (current?.hasNext() != true && parents.isNotEmpty()) {
+            current = parents.removeAt(0)
+        }
+    }
+
+    override fun hasNext(): Boolean {
+        cycleIfNecessary()
+        return current?.hasNext() == true
+    }
+
+    override fun next(): T {
+        cycleIfNecessary()
+        return current?.next() ?: throw NoSuchElementException()
+    }
+}
diff --git a/lib/src/test/kotlin/de/linkel/aoc/utils/IntRangeMixInTest.kt b/lib/src/test/kotlin/de/linkel/aoc/utils/IntRangeMixInTest.kt
new file mode 100644
index 0000000..56f54b6
--- /dev/null
+++ b/lib/src/test/kotlin/de/linkel/aoc/utils/IntRangeMixInTest.kt
@@ -0,0 +1,118 @@
+package de.linkel.aoc.utils
+
+import org.assertj.core.api.Assertions
+import org.junit.jupiter.api.Test
+
+class IntRangeMixInTest {
+    @Test
+    fun `1 to 3 and 4 to 6 do not intersect`() {
+        Assertions.assertThat(
+            (1..3).intersects(4..6)
+        ).isFalse()
+    }
+
+    @Test
+    fun `10 to 30 and 4 to 6 do not intersect`() {
+        Assertions.assertThat(
+            (10..30).intersects(4..6)
+        ).isFalse()
+    }
+
+    @Test
+    fun `1 to 3 and 2 to 4 intersect`() {
+        Assertions.assertThat(
+            (1..3).intersects(2..4)
+        ).isTrue()
+    }
+
+    @Test
+    fun `1 to 3 and 3 to 4 intersect`() {
+        Assertions.assertThat(
+            (1..3).intersects(3..4)
+        ).isTrue()
+    }
+
+    @Test
+    fun `-1 to 1 and 0 to 4 intersect`() {
+        Assertions.assertThat(
+            (-1..1).intersects(0..4)
+        ).isTrue()
+    }
+
+    @Test
+    fun `-3 to -1 and -2 to 4 intersect`() {
+        Assertions.assertThat(
+            (-3..-1).intersects(-2..4)
+        ).isTrue()
+    }
+
+    @Test
+    fun `1 to 5 and 5 to 10 intersect`() {
+        Assertions.assertThat(
+            (1..5).intersects(5..10)
+        ).isTrue()
+    }
+
+    @Test
+    fun `1 to 5 and 4 to 5 intersect`() {
+        Assertions.assertThat(
+            (1..5).intersects(4..5)
+        ).isTrue()
+    }
+
+    @Test
+    fun `1 to 5 and 3 to 4 intersect`() {
+        Assertions.assertThat(
+            (1..5).intersects(3..4)
+        ).isTrue()
+    }
+
+    @Test
+    fun `1 to 5 and 5 to 5 intersect`() {
+        Assertions.assertThat(
+            (1..5).intersects(5..5)
+        ).isTrue()
+    }
+
+    @Test
+    fun `2 to 4 extended by 1 at front is 1 to 4`() {
+        Assertions.assertThat(
+            (2..4).extend(front = 1)
+        ).isEqualTo(1..4)
+    }
+
+    @Test
+    fun `2 to 4 extended by 2 at front is 0 to 4`() {
+        Assertions.assertThat(
+            (2..4).extend(front = 2)
+        ).isEqualTo(0..4)
+    }
+
+    @Test
+    fun `2 to 4 extended by 3 at front is -1 to 4`() {
+        Assertions.assertThat(
+            (2..4).extend(front = 3)
+        ).isEqualTo(-1..4)
+    }
+
+    @Test
+    fun `2 to 4 extended by 1 at back is 2 to 5`() {
+        Assertions.assertThat(
+            (2..4).extend(back = 1)
+        ).isEqualTo(2..5)
+    }
+
+    @Test
+    fun `2 to 4 extended by 2 at back is 2 to 6`() {
+        Assertions.assertThat(
+            (2..4).extend(back = 2)
+        ).isEqualTo(2..6)
+    }
+
+    @Test
+    fun `2 to 4 extended by 2 at front and back is 0 to 6`() {
+        Assertions.assertThat(
+            (2..4).extend(front = 2, back = 2)
+        ).isEqualTo(0..6)
+    }
+}
diff --git a/lib/src/test/kotlin/de/linkel/aoc/utils/SequenceConcatTest.kt b/lib/src/test/kotlin/de/linkel/aoc/utils/SequenceConcatTest.kt
new file mode 100644
index 0000000..851d7f7
--- /dev/null
+++ b/lib/src/test/kotlin/de/linkel/aoc/utils/SequenceConcatTest.kt
@@ -0,0 +1,69 @@
+package de.linkel.aoc.utils
+
+import org.assertj.core.api.Assertions
+import org.junit.jupiter.api.Test
+
+class SequenceConcatTest {
+    @Test
+    fun `1,2,3 can be prepended with 0`() {
+        Assertions.assertThat(
+            sequenceOf(1, 2, 3).prepend(0).toList()
+        ).isEqualTo(listOf(0,1,2,3))
+    }
+
+    @Test
+    fun `1,2,3 can be extended with 4`() {
+        Assertions.assertThat(
+            sequenceOf(1, 2, 3).append(4).toList()
+        ).isEqualTo(listOf(1,2,3,4))
+    }
+
+    @Test
+    fun `1,2,3 can be prepended with 0 and extended with 4`() {
+        Assertions.assertThat(
+            sequenceOf(1, 2, 3).prepend(0).append(4).toList()
+        ).isEqualTo(listOf(0,1,2,3,4))
+    }
+
+    @Test
+    fun `1,2,3 can be extended with 4 and prepended with 0`() {
+        Assertions.assertThat(
+            sequenceOf(1, 2, 3).append(4).prepend(0).toList()
+        ).isEqualTo(listOf(0,1,2,3,4))
+    }
+
+    @Test
+    fun `1,2,3 can be prepended with -1,0`() {
+        Assertions.assertThat(
+            sequenceOf(1, 2, 3).prepend(sequenceOf(-1,0)).toList()
+        ).isEqualTo(listOf(-1,0,1,2,3))
+    }
+
+    @Test
+    fun `1,2,3 can be extended with 4,5`() {
+        Assertions.assertThat(
+            sequenceOf(1, 2, 3).append(sequenceOf(4,5)).toList()
+        ).isEqualTo(listOf(1,2,3,4,5))
+    }
+
+    @Test
+    fun `1,2 + 3 can be extended with 4 and prepended with 0`() {
+        Assertions.assertThat(
+            sequenceOf(1, 2).append(3).append(4).prepend(0).toList()
+        ).isEqualTo(listOf(0,1,2,3,4))
+    }
+
+    @Test
+    fun `1,2 + 3 can be extended with 4,5 and prepended with -1,0`() {
+        Assertions.assertThat(
+            sequenceOf(1, 2).append(3).append(sequenceOf(4,5)).prepend(sequenceOf(-1,0)).toList()
+        ).isEqualTo(listOf(-1,0,1,2,3,4,5))
+    }
+
+    @Test
+    fun `0,1 + 2,3 + 4,5 works`() {
+        Assertions.assertThat(
+            (sequenceOf(0, 1) + sequenceOf(2, 3) + sequenceOf(4, 5)).toList()
+        ).isEqualTo(listOf(0,1,2,3,4,5))
+    }
+}
diff --git a/lib/src/test/kotlin/de/linkel/aoc/utils/TopListTest.kt b/lib/src/test/kotlin/de/linkel/aoc/utils/TopListTest.kt
index 4955b10..0330e8d 100644
--- a/lib/src/test/kotlin/de/linkel/aoc/utils/TopListTest.kt
+++ b/lib/src/test/kotlin/de/linkel/aoc/utils/TopListTest.kt
@@ -5,8 +5,28 @@ import org.junit.jupiter.api.Test
 
 class TopListTest {
     @Test
-    fun `top 3 list with 3 elements works`() {
-        val top3 = TopList<Int>(3).plus(listOf(1, 2, 5, 3, 4)).toList()
+    fun `empty top 3 list works`() {
+        val top3 = TopList<Int>(3)
+        Assertions.assertThat(top3).hasSize(0)
+        Assertions.assertThat(top3.isEmpty()).isTrue()
+    }
+
+    @Test
+    fun `default collection methods work`() {
+        val top3 = TopList<Int>(3).plus(listOf(1, 2, 5, 3, 4))
+        Assertions.assertThat(top3).hasSize(3)
+        Assertions.assertThat(top3).contains(5)
+        Assertions.assertThat(top3).contains(4)
+        Assertions.assertThat(top3).contains(3)
+        Assertions.assertThat(top3.isEmpty()).isFalse()
+        Assertions.assertThat(top3.contains(3)).isTrue()
+        Assertions.assertThat(top3.containsAll(listOf(5, 4))).isTrue()
+        Assertions.assertThat(top3.first()).isEqualTo(5)
+    }
+
+    @Test
+    fun `top 3 list with 3 elements in 2 batches works`() {
+        val top3 = TopList<Int>(3).plus(listOf(1, 2, 5)).plus(listOf(3, 4)).toList()
         Assertions.assertThat(top3).hasSize(3)
         Assertions.assertThat(top3).contains(5)
         Assertions.assertThat(top3).contains(4)
@@ -16,6 +36,13 @@ class TopListTest {
 
     @Test
     fun `top 3 list with 1 element works`() {
+        val top3 = TopList<Int>(3).plus(23).toList()
+        Assertions.assertThat(top3).hasSize(1)
+        Assertions.assertThat(top3).contains(23)
+    }
+
+    @Test
+    fun `top 3 list with 1 element in list works`() {
         val top3 = TopList<Int>(3).plus(listOf(23)).toList()
         Assertions.assertThat(top3).hasSize(1)
         Assertions.assertThat(top3).contains(23)
diff --git a/lib/src/test/kotlin/de/linkel/aoc/utils/grid/AreaTest.kt b/lib/src/test/kotlin/de/linkel/aoc/utils/grid/AreaTest.kt
new file mode 100644
index 0000000..eb13bdd
--- /dev/null
+++ b/lib/src/test/kotlin/de/linkel/aoc/utils/grid/AreaTest.kt
@@ -0,0 +1,72 @@
+package de.linkel.aoc.utils.grid
+
+import org.assertj.core.api.Assertions
+import org.junit.jupiter.api.Test
+
+class AreaTest {
+    @Test
+    fun `basic properties work`() {
+        val area = Area(1, 2, 10, 5)
+        Assertions.assertThat(area.origin).isEqualTo(Point(1, 2))
+        Assertions.assertThat(area.northWest).isEqualTo(Point(1, 2))
+        Assertions.assertThat(area.northEast).isEqualTo(Point(10, 2))
+        Assertions.assertThat(area.southWest).isEqualTo(Point(1, 6))
+        Assertions.assertThat(area.southEast).isEqualTo(Point(10, 6))
+        Assertions.assertThat(area.dimension).isEqualTo(Dimension(10, 5))
+    }
+
+    @Test
+    fun `can extend to into east`() {
+        val area = Area(0, 0, 3, 3).extendTo(Point(5, 1))
+        Assertions.assertThat(area.origin).isEqualTo(Point(0, 0))
+        Assertions.assertThat(area.northWest).isEqualTo(Point(0, 0))
+        Assertions.assertThat(area.northEast).isEqualTo(Point(5, 0))
+        Assertions.assertThat(area.southWest).isEqualTo(Point(0, 2))
+        Assertions.assertThat(area.southEast).isEqualTo(Point(5, 2))
+        Assertions.assertThat(area.dimension).isEqualTo(Dimension(6, 3))
+    }
+
+    @Test
+    fun `can extend to into west`() {
+        val area = Area(0, 0, 3, 3).extendTo(Point(-1, 1))
+        Assertions.assertThat(area.origin).isEqualTo(Point(-1, 0))
+        Assertions.assertThat(area.northWest).isEqualTo(Point(-1, 0))
+        Assertions.assertThat(area.northEast).isEqualTo(Point(2, 0))
+        Assertions.assertThat(area.southWest).isEqualTo(Point(-1, 2))
+        Assertions.assertThat(area.southEast).isEqualTo(Point(2, 2))
+        Assertions.assertThat(area.dimension).isEqualTo(Dimension(4, 3))
+    }
+
+    @Test
+    fun `can extend to into north`() {
+        val area = Area(0, 0, 3, 3).extendTo(Point(0, -1))
+        Assertions.assertThat(area.origin).isEqualTo(Point(0, -1))
+        Assertions.assertThat(area.northWest).isEqualTo(Point(0, -1))
+        Assertions.assertThat(area.northEast).isEqualTo(Point(2, -1))
+        Assertions.assertThat(area.southWest).isEqualTo(Point(0, 2))
+        Assertions.assertThat(area.southEast).isEqualTo(Point(2, 2))
+        Assertions.assertThat(area.dimension).isEqualTo(Dimension(3, 4))
+    }
+
+    @Test
+    fun `can extend to into south`() {
+        val area = Area(0, 0, 3, 3).extendTo(Point(0, 3))
+        Assertions.assertThat(area.origin).isEqualTo(Point(0, 0))
+        Assertions.assertThat(area.northWest).isEqualTo(Point(0, 0))
+        Assertions.assertThat(area.northEast).isEqualTo(Point(2, 0))
+        Assertions.assertThat(area.southWest).isEqualTo(Point(0, 3))
+        Assertions.assertThat(area.southEast).isEqualTo(Point(2, 3))
+        Assertions.assertThat(area.dimension).isEqualTo(Dimension(3, 4))
+    }
+
+    @Test
+    fun `can be moved`() {
+        val area = Area(0, 0, 3, 3).plus(Vector(2, 1))
+        Assertions.assertThat(area.origin).isEqualTo(Point(2, 1))
+        Assertions.assertThat(area.northWest).isEqualTo(Point(2, 1))
+        Assertions.assertThat(area.northEast).isEqualTo(Point(4, 1))
+        Assertions.assertThat(area.southWest).isEqualTo(Point(2, 3))
+        Assertions.assertThat(area.southEast).isEqualTo(Point(4, 3))
+        Assertions.assertThat(area.dimension).isEqualTo(Dimension(3, 3))
+    }
+}
diff --git a/lib/src/test/kotlin/de/linkel/aoc/utils/grid/PointTest.kt b/lib/src/test/kotlin/de/linkel/aoc/utils/grid/PointTest.kt
new file mode 100644
index 0000000..6b0dedb
--- /dev/null
+++ b/lib/src/test/kotlin/de/linkel/aoc/utils/grid/PointTest.kt
@@ -0,0 +1,27 @@
+package de.linkel.aoc.utils.grid
+
+import org.assertj.core.api.Assertions
+import org.junit.jupiter.api.Test
+
+class PointTest {
+    @Test
+    fun `basic properties work`() {
+        val point = Point(1, 2)
+        Assertions.assertThat(point.x).isEqualTo(1)
+        Assertions.assertThat(point.y).isEqualTo(2)
+    }
+
+    @Test
+    fun `can be moved`() {
+        val point = Point(1, 2) + Vector(2, -1)
+        Assertions.assertThat(point.x).isEqualTo(3)
+        Assertions.assertThat(point.y).isEqualTo(1)
+    }
+
+    @Test
+    fun `2 points form a vector`() {
+        val vector = Point(1, 2) - Point(1,1)
+        Assertions.assertThat(vector.deltaX).isEqualTo(0)
+        Assertions.assertThat(vector.deltaY).isEqualTo(1)
+    }
+}