diff --git a/bombadil.toml b/bombadil.toml
index 48a80a6..02537e9 100644
--- a/bombadil.toml
+++ b/bombadil.toml
@@ -19,13 +19,15 @@ discord = { source = "config/electron-flags.conf", target = ".config/discord-fla
 1password = { source = "autostart/1password.desktop", target = ".config/autostart/1password.desktop", direct = true }
 megasync = { source = "autostart/megasync.desktop", target = ".config/autostart/megasync.desktop", direct = true }
 
-# Also needs a one-time `systemctl --user enable --now eww-daemon.service eww-bars.service ip-geolocation.service sunset.timer swww-daemon.service'
+# Also needs a one-time `systemctl --user enable --now eww-daemon.service eww-bars.service ip-geolocation.service sunset.timer swww-daemon.service wallpaper.timer'
 eww-daemon = { source = "systemd/eww-daemon.service", target = ".config/systemd/user/eww-daemon.service", direct = true }
 eww-bars = { source = "systemd/eww-bars.service", target = ".config/systemd/user/eww-bars.service" }
 ip-geolocation = { source = "systemd/ip-geolocation.service", target = ".config/systemd/user/ip-geolocation.service", direct = true }
 sunset-service = { source = "systemd/sunset.service", target = ".config/systemd/user/sunset.service", direct = true }
 sunset-timer = { source = "systemd/sunset.timer", target = ".config/systemd/user/sunset.timer", direct = true }
 swww-daemon = { source = "systemd/swww-daemon.service", target = ".config/systemd/user/swww-daemon.service", direct = true }
+wallpaper-service = { source = "systemd/wallpaper.service", target = ".config/systemd/user/wallpaper.service", direct = true }
+wallpaper-timer = { source = "systemd/wallpaper.timer", target = ".config/systemd/user/wallpaper.timer", direct = true }
 
 btop = { source = "btop", target = ".config/btop", direct = true }
 dunst = { source = "dunst", target = ".config/dunst", direct = true }
diff --git a/eww/eww.yuck b/eww/eww.yuck
index dc58e80..539a155 100644
--- a/eww/eww.yuck
+++ b/eww/eww.yuck
@@ -120,7 +120,7 @@
 ;(defwidget colour_selector []
   ;(clicker :text "" :command "uwsm-app -- hyprpicker -a"))
 (defwidget wallpaper []
-  (clicker :text "󰸉" :command "~/scripts/swww_change.py"))
+  (clicker :text "󰸉" :command "~/.config/eww/scripts/wallpaper-shell"))
 (defwidget sunset []
   (clicker :text "" :command "python -OO ~/scripts/sunset.py"))
 
diff --git a/eww/scripts/wallpaper-shell b/eww/scripts/wallpaper-shell
new file mode 100755
index 0000000..daa799a
--- /dev/null
+++ b/eww/scripts/wallpaper-shell
@@ -0,0 +1,4 @@
+#!/bin/env sh
+
+# EWW doesn't seem to like listening to Python scripts directly, but this wrapper seems to work fine
+python -OO ~/scripts/wallpaper.py
diff --git a/scripts/lib/swww.py b/scripts/lib/swww.py
deleted file mode 100644
index 394ba01..0000000
--- a/scripts/lib/swww.py
+++ /dev/null
@@ -1,45 +0,0 @@
-"""Basic functions for interacting with swww"""
-from json import loads
-from pathlib import Path
-from random import sample
-from shlex import split
-from socket import gethostname
-from subprocess import run
-
-
-IS_DESKTOP = gethostname() == "chonk"
-
-MONITORS = ("DP-1", "DP-2") if IS_DESKTOP else ("eDP-1",)
-
-ANGLE_TRANSITION_ARGS = [
-	"--transition-type", "wipe",
-	"--transition-angle", "30",
-	"--transition-step", "45",
-	"--transition-fps", "165" if IS_DESKTOP else "120",
-]
-IMMEDIATE_TRANSITION_ARGS = [
-	"--transition-step", "255",
-]
-
-
-def _run_cmd(arg0: str, *args: str) -> str:
-	return run([arg0, *args] if args else split(arg0), capture_output=True).stdout.decode("utf-8")
-
-
-def monitors() -> list[str]:
-	return [monitor["name"] for monitor in loads(_run_cmd("hyprctl monitors -j"))]
-
-
-def run_swww(monitor: str, image: Path, extra_args: list[str] | None = None) -> None:
-	run(["swww", "img", "-o", monitor, image, *(extra_args or [])])
-
-
-def get_wallpapers() -> list[Path]:
-	return list(Path("~/Pictures/wallpapers/").expanduser().glob("*"))
-
-
-def sample_wallpapers(displays: list[str] | None = None) -> "zip[tuple[str, Path]]":
-	if displays is None:
-		displays = monitors()
-	return zip(displays, sample(get_wallpapers(), len(displays)))
-
diff --git a/scripts/lib/wallpaper.py b/scripts/lib/wallpaper.py
new file mode 100644
index 0000000..4d633ba
--- /dev/null
+++ b/scripts/lib/wallpaper.py
@@ -0,0 +1,216 @@
+"""Script to update the wallpaper"""
+from abc import ABC, abstractmethod
+from json import dumps, loads
+from math import ceil, floor, isnan, nan
+from os import environ
+from pathlib import Path
+from random import sample
+from re import Pattern, compile, match
+from subprocess import run
+from time import sleep
+from typing import cast, override
+
+from .evening import on_steam, sunup_amount
+
+
+# Python sets aren't insertion-ordered, but dict keys are
+type OrderedSet[T] = dict[T, None]
+
+
+class Background(ABC):
+	_colour: Pattern[str] = compile(r"^[a-fA-F0-9]{6}$")
+
+	@abstractmethod
+	def blue_light(self) -> float: ...
+
+	@abstractmethod
+	@override
+	def __eq__(self, value: object, /) -> bool: ...
+
+	@abstractmethod
+	@override
+	def __hash__(self) -> int: ...
+
+	@abstractmethod
+	@override
+	def __str__(self) -> str: ...
+
+	@classmethod
+	def parse(cls, arg: str) -> "Background":
+		if match(cls._colour, arg):
+			return Colour(int(arg, 16))
+		else:
+			return Wallpaper(Path(arg))
+
+
+class Wallpaper(Background):
+	_cache: Path = Path(environ["XDG_CACHE_HOME"]) / "wallpaper_blue_light.json"
+	_wallpapers: Path = Path("~/Pictures/wallpapers/").expanduser()
+
+	def __init__(self, image: Path) -> None:
+		self._path: Path = image
+		self._blue_light: float = nan
+
+	def _calculate_blue_light(self) -> float:
+		from PIL import Image
+		data = cast(list[int], Image.open(self._path).getdata(2))
+		return sum(data) / len(data)
+
+	@classmethod
+	def _read_cache(cls) -> dict[str, float]:
+		if cls._cache.exists():
+			if (text := cls._cache.read_text().strip()):
+				if isinstance((obj := loads(text)), dict):
+					return cast(dict[str, float], obj)
+		return {}
+
+	@classmethod
+	def _write_cache(cls, cache: dict[str, float]) -> None:
+		stringified = dumps(cache)
+		if len(stringified) != cls._cache.write_text(stringified):
+			raise Exception("Did not fully write blue light cache to file")
+
+	@classmethod
+	def available(cls) -> "OrderedSet[Background]":
+		cache = cls._read_cache()
+		modified = False
+		wallpapers = {str(path): Wallpaper(path) for path in cls._wallpapers.iterdir()}
+		for wallpaper in wallpapers.values():
+			cached = cache.get(str(wallpaper._path))
+			if cached is None or isnan(cached):
+				print("New file:", wallpaper._path)
+				cached = wallpaper._calculate_blue_light()
+				modified = True
+				cache[str(wallpaper._path)] = cached
+			wallpaper._blue_light = cached
+		if modified:
+			cache = {path: score for (path, score) in sorted(cache.items(), key=lambda pair: pair[1])}
+			cls._write_cache(cache)
+		return {wallpapers[path]: None for path in cache.keys()}
+
+	@override
+	def blue_light(self) -> float:
+		return self._blue_light
+
+	@override
+	def __eq__(self, value: object, /) -> bool:
+		if isinstance(value, Wallpaper):
+			return self._path == value._path
+		return False
+
+	@override
+	def __hash__(self) -> int:
+		return hash(self._path)
+
+	@override
+	def __str__(self) -> str:
+		return str(self._path)
+
+	@override
+	def __repr__(self) -> str:
+		return f"Wallpaper({repr(self._path)})"
+
+
+class Colour(Background):
+	def __init__(self, value: int) -> None:
+		self._value: int = value
+
+	@override
+	def blue_light(self) -> float:
+		return self._value & 0xFF
+
+	@override
+	def __eq__(self, value: object, /) -> bool:
+		if isinstance(value, Colour):
+			return self._value == value._value
+		return False
+
+	@override
+	def __hash__(self) -> int:
+		return hash(self._value)
+
+	@override
+	def __str__(self) -> str:
+		return hex(self._value)
+
+	@override
+	def __repr__(self) -> str:
+		return f"Colour({hex(self._value)})"
+
+
+def _convert_bytes(output: bytes) -> str:
+	return output.decode("utf-8").strip()
+
+
+def _swww_cmd(*args: str) -> str:
+	output = run(["swww", *args], capture_output=True)
+	if output.stderr:
+		raise Exception(f"swww returned: '{_convert_bytes(output.stderr)}'")
+	return _convert_bytes(output.stdout)
+
+
+class Monitor:
+	_query: Pattern[str] = compile(r"^([^:]+): (\d+)x(\d+), scale: ([\d.]+), currently displaying: (?:image|color): (.+)$")
+	_transition_args: list[str] = [
+		"--transition-type=wipe",
+		"--transition-angle=30",
+		"--transition-step=45",
+		"--transition-fps=120",
+	]
+
+	def __init__(self, line: str) -> None:
+		if not (values := match(self._query, line)):
+			raise Exception(f"Failed to extract information from: '{line}'")
+		self._name: str = values[1]
+		self._resolution: tuple[int, int] = (int(values[2]), int(values[3]))
+		self._scale: float = float(values[4])
+		self._background: Background = Background.parse(values[5])
+
+	def is_colour(self) -> bool:
+		return isinstance(self._background, Colour)
+
+	def set_wallpaper(self, background: Background) -> None:
+		self._background = background
+		_ = _swww_cmd("img", *self._transition_args, f"--outputs={self._name}", str(self._background))
+
+	def get_background(self) -> Background:
+		return self._background
+
+	@classmethod
+	def current(cls) -> "list[Monitor]":
+		return [Monitor(line) for line in _swww_cmd("query").splitlines()]
+
+	@override
+	def __eq__(self, value: object, /) -> bool:
+		if isinstance(value, Monitor):
+			return self._background == value._background
+		return False
+
+	@override
+	def __repr__(self) -> str:
+		return f"Monitor('{self._name}: {self._resolution[0]}x{self._resolution[1]}, scale: {self._scale}, currently displaying: {"color" if self.is_colour() else "image"}: {self._background}')"
+
+	@override
+	def __str__(self) -> str:
+		return f"{self._name}: {self._background}"
+
+
+def select_wallpapers(available: list[Background]) -> list[Background]:
+	radius = len(available) / 3
+	centre = sunup_amount() * len(available)
+	return available[max(0, floor(centre - radius)): min(len(available) + 1, ceil(centre + radius))]
+
+
+def main(check_steam: bool = False) -> None:
+	if check_steam and on_steam():
+		return
+
+	monitors = Monitor.current()
+	wallpapers = Wallpaper.available()
+
+	for monitor in monitors:
+		wallpapers.pop(monitor.get_background(), None)
+
+	for monitor, wallpaper in zip(monitors, sample(select_wallpapers(list(wallpapers.keys())), len(monitors))):
+		monitor.set_wallpaper(wallpaper)
+		sleep(1.25)
diff --git a/scripts/swww_change.py b/scripts/swww_change.py
deleted file mode 100755
index 7483f5e..0000000
--- a/scripts/swww_change.py
+++ /dev/null
@@ -1,9 +0,0 @@
-#!/bin/env python
-"""Selects new backgrounds for the monitors"""
-
-from lib.swww import ANGLE_TRANSITION_ARGS, run_swww, sample_wallpapers
-
-
-for monitor, wallpaper in sample_wallpapers():
-	run_swww(monitor, wallpaper, ANGLE_TRANSITION_ARGS)
-
diff --git a/scripts/swww_set.py b/scripts/swww_set.py
deleted file mode 100755
index 299c1f6..0000000
--- a/scripts/swww_set.py
+++ /dev/null
@@ -1,9 +0,0 @@
-#!/bin/env python
-"""Sets a new background for the monitors immediately"""
-
-from lib.swww import IMMEDIATE_TRANSITION_ARGS, run_swww, sample_wallpapers
-
-
-for monitor, wallpaper in sample_wallpapers():
-	run_swww(monitor, wallpaper, IMMEDIATE_TRANSITION_ARGS)
-
diff --git a/scripts/wallpaper.py b/scripts/wallpaper.py
new file mode 100755
index 0000000..4c20b21
--- /dev/null
+++ b/scripts/wallpaper.py
@@ -0,0 +1,20 @@
+#!/bin/env python
+from argparse import ArgumentParser, Namespace
+from typing import cast
+
+from lib.wallpaper import main
+
+
+class Arguments(Namespace):
+	check_steam: bool = False
+
+
+def call_from_args() -> None:
+	parser = ArgumentParser(description="Adjusts the wallpaper based on the time of day")
+	_ = parser.add_argument("-s", "--check-steam", action="store_true", help="Don't adjust the wallpaper if Steam is active")
+	args = cast(Arguments, parser.parse_args())
+	main(args.check_steam)
+
+
+if __name__ == "__main__":
+	call_from_args()
diff --git a/systemd/wallpaper.service b/systemd/wallpaper.service
new file mode 100644
index 0000000..ec66bfb
--- /dev/null
+++ b/systemd/wallpaper.service
@@ -0,0 +1,6 @@
+[Unit]
+Description=Sets the wallpaper based on the time of day
+
+[Service]
+Type=oneshot
+ExecStart=/bin/env python -OO /home/mbradley/scripts/wallpaper.py --check-steam
diff --git a/systemd/wallpaper.timer b/systemd/wallpaper.timer
new file mode 100644
index 0000000..14081a9
--- /dev/null
+++ b/systemd/wallpaper.timer
@@ -0,0 +1,12 @@
+[Unit]
+Description=Changes the wallpaper over the course of the day to ease eye strain
+After=graphical-session.target
+After=swww-daemon.service
+
+[Timer]
+OnCalendar=*:0/15
+Persistent=true
+AccuracySec=5s
+
+[Install]
+WantedBy=timers.target