diff --git a/roll/roll.py b/roll/roll.py
index 03b0488..d6ac444 100644
--- a/roll/roll.py
+++ b/roll/roll.py
@@ -12,13 +12,13 @@ ROLL_PATTERN = re.compile(r"(\d+)d(\d+)([+-]\d+)?")
 
 @dataclasses.dataclass(frozen=True)
 class Roll:
-    """A roll of one or more dice"""
+    """a roll of one or more dice"""
 
-    dice_count: int
-    sides: int
+    dice_count: int = 1
+    sides: int = 20
     modifier: int | None = None
 
-    def __post_init__(self):
+    def __post_init__(self) -> None:
         if self.dice_count < 1:
             msg = "dice must be greater than 0"
             raise ValueError(msg)
@@ -28,7 +28,7 @@ class Roll:
 
     @classmethod
     def from_str(cls, value: str) -> Self:
-        """Parse a Roll from it's short representation, e.g. 2d6 or 1d20-2"""
+        """parse a Roll from its short representation, e.g. 2d6 or 1d20-2"""
         match = ROLL_PATTERN.fullmatch(value)
         if match is None:
             msg = f"expected {value!r} to match pattern {ROLL_PATTERN.pattern!r}"
@@ -37,21 +37,21 @@ class Roll:
         return cls(int(dice_count), int(sides), int(modifier) if modifier else None)
 
     def modifier_str(self) -> str:
-        """Return the modifier as a string"""
+        """return the modifier as a string"""
         if self.modifier is None:
             return ""
         sign = "+" if self.modifier > 0 else ""
         return f"{sign}{self.modifier}"
 
     def to_str(self) -> str:
-        """Return the short representation of a roll, e.g. 3d4 or 2d20+3"""
+        """return the short representation of a roll, e.g. 3d4 or 2d20+3"""
         return f"{self.dice_count}d{self.sides}{self.modifier_str()}"
 
     def modify(self, modifier: int) -> Self:
-        """Return a new Roll with the given modifier"""
+        """return a new Roll with the given modifier"""
         return dataclasses.replace(self, modifier=modifier)
 
     def throw(self) -> Throw:
-        """Throw the dice"""
+        """throw the dice"""
         throw = [random.randint(1, self.sides) for _ in range(self.dice_count)]
-        return Throw(throw, self.modifier)
+        return Throw(throw, self.sides, self.modifier)
diff --git a/roll/throw.py b/roll/throw.py
index 0c00d76..ce38119 100644
--- a/roll/throw.py
+++ b/roll/throw.py
@@ -1,12 +1,25 @@
 import dataclasses
 
+D20_MAX = 20
+
 
 @dataclasses.dataclass(frozen=True)
 class Throw:
     results: list[int]
-    modifier: int | None
+    sides: int
+    modifier: int | None = None
 
     @property
     def total(self) -> int:
-        """Calculate the total of the throw, accounting for the modifier"""
+        """calculate the total of the throw, accounting for the modifier"""
         return sum(self.results) + (self.modifier or 0)
+
+    @property
+    def is_critical_hit(self) -> bool:
+        """check if the throw is a 20 on a 1d20"""
+        return self.sides == D20_MAX and self.results == [D20_MAX]
+
+    @property
+    def is_critical_miss(self) -> bool:
+        """check if the throw is a 1 on a 1d20"""
+        return self.sides == D20_MAX and self.results == [1]
diff --git a/tests/roll_test.py b/tests/roll_test.py
index af5bf3b..eaec67c 100644
--- a/tests/roll_test.py
+++ b/tests/roll_test.py
@@ -1,4 +1,4 @@
-import pytest  # type: ignore (TODO: figure out why pyright can't import pytest)
+import pytest
 
 from roll.roll import Roll
 
@@ -11,7 +11,8 @@ def test_roll_validation():
 
 
 @pytest.mark.parametrize(
-    ("roll", "expected"), [(Roll(1, 20), "1d20"), (Roll(2, 20, 3), "2d20+3"), (Roll(4, 6, -3), "4d6-3")]
+    ("roll", "expected"),
+    [(Roll(1, 20), "1d20"), (Roll(2, 20, 3), "2d20+3"), (Roll(4, 6, -3), "4d6-3")],
 )
 def test_str_roundtrip(roll: Roll, expected: str):
     assert roll.to_str() == expected
@@ -29,7 +30,7 @@ def test_modify():
     modified_roll = roll.modify(3)
     assert modified_roll == Roll(2, 20, 3)
     assert roll == Roll(2, 20)
-    assert modified_roll is not roll
+    assert modified_roll is not roll and modified_roll != roll
 
 
 @pytest.mark.parametrize("n", list(range(1, 5)))
diff --git a/tests/throw_test.py b/tests/throw_test.py
new file mode 100644
index 0000000..a94d7de
--- /dev/null
+++ b/tests/throw_test.py
@@ -0,0 +1,29 @@
+from roll.throw import Throw
+
+
+def test_throw():
+    throw = Throw([1, 2, 3], sides=4)
+    assert throw.total == 6
+    assert not throw.is_critical_hit
+    assert not throw.is_critical_miss
+
+
+def test_throw_with_modifier():
+    throw = Throw([1, 2, 3], sides=4, modifier=5)
+    assert throw.total == 11
+    assert not throw.is_critical_hit
+    assert not throw.is_critical_miss
+
+
+def test_critical_hit():
+    throw = Throw([20], sides=20)
+    assert throw.total == 20
+    assert throw.is_critical_hit
+    assert not throw.is_critical_miss
+
+
+def test_critical_miss():
+    throw = Throw([1], sides=20)
+    assert throw.total == 1
+    assert not throw.is_critical_hit
+    assert throw.is_critical_miss