diff --git a/tests/test_physics.py b/tests/test_physics.py
new file mode 100644
index 0000000..d0aaa05
--- /dev/null
+++ b/tests/test_physics.py
@@ -0,0 +1,76 @@
+import pytest
+
+from game import constants
+from tests.support import makeWorld, stepWorld, settle
+from game.sim.inputCommand import InputCommand
+
+
+def test_gravityAppliesWhenAirborne():
+    world = makeWorld([
+        "      ",
+        " p    ",
+        "      ",
+        "      ",
+        "XXXXXX",
+    ])
+    world.step(InputCommand())
+    assert world.player.vy == pytest.approx(constants.gravity)
+
+
+def test_playerLandsOnGround():
+    world = makeWorld([
+        "      ",
+        " p    ",
+        "      ",
+        "XXXXXX",
+    ])
+    settle(world, 40)
+    player = world.player
+    assert player.onGround
+    assert player.vy == 0.0
+    assert player.bottom == pytest.approx(48.0)
+
+
+def test_fallSpeedIsCapped():
+    tall = ["          "] * 40
+    tall[1] = " p        "
+    tall.append("XXXXXXXXXX")
+    world = makeWorld(tall)
+    maxSeen = 0.0
+    for _ in range(35):
+        world.step(InputCommand())
+        maxSeen = max(maxSeen, world.player.vy)
+    assert maxSeen <= constants.maxFallSpeed + 1e-6
+    assert maxSeen == pytest.approx(constants.maxFallSpeed)
+
+
+def test_wallBlocksHorizontalMovement():
+    world = makeWorld([
+        "   #",
+        " p #",
+        "XXXX",
+    ])
+    stepWorld(world, 40, right=True, run=True)
+    player = world.player
+    wallLeft = 3 * constants.tileSize
+    limit = wallLeft - player.w
+    assert player.x <= limit + 0.01
+    assert player.vx == 0.0
+    assert player.onWallRight
+
+
+def test_ceilingStopsUpwardMovement():
+    world = makeWorld([
+        "XXXX",
+        "    ",
+        " p  ",
+        "XXXX",
+    ])
+    hitCeiling = False
+    world.step(InputCommand(jump=True, jumpHeld=True))
+    for _ in range(12):
+        world.step(InputCommand(jumpHeld=True))
+        if world.player.onCeiling:
+            hitCeiling = True
+            assert world.player.top >= constants.tileSize - 0.01
+    assert hitCeiling
diff --git a/tests/test_player.py b/tests/test_player.py
new file mode 100644
index 0000000..ef1e461
--- /dev/null
+++ b/tests/test_player.py
@@ -0,0 +1,165 @@
+import pytest
+
+from game import constants
+from tests.support import makeWorld, settle
+from game.sim.inputCommand import InputCommand
+
+
+ledgeLevel = [
+    "        ",
+    "        ",
+    " p      ",
+    "XXX     ",
+]
+
+flatLevel = [
+    " p      ",
+    "        ",
+    "XXXXXXXX",
+]
+
+wallLevel = [
+    "    #",
+    "    #",
+    "    #",
+    "    #",
+    "XXXXX",
+]
+
+
+def walkOffLedge(world):
+    for _ in range(40):
+        world.step(InputCommand(right=True, run=True))
+        if not world.player.onGround:
+            return True
+    return False
+
+
+def test_coyoteJumpKeepsAirJump():
+    world = makeWorld(ledgeLevel)
+    assert walkOffLedge(world)
+    world.step(InputCommand(right=True, jump=True, jumpHeld=True))
+    player = world.player
+    assert player.vy == pytest.approx(constants.jumpVelocity + constants.gravity)
+    assert player.airJumps == constants.maxAirJumps
+
+
+def test_afterCoyoteExpiresJumpIsDoubleJump():
+    world = makeWorld(ledgeLevel)
+    assert walkOffLedge(world)
+    for _ in range(constants.coyoteFrames + 2):
+        world.step(InputCommand())
+    world.step(InputCommand(jump=True, jumpHeld=True))
+    player = world.player
+    assert player.airJumps == 0
+    assert player.vy == pytest.approx(constants.doubleJumpVelocity + constants.gravity)
+
+
+def test_doubleJumpConsumesAirJump():
+    world = makeWorld(flatLevel)
+    settle(world, 20)
+    world.step(InputCommand(jump=True, jumpHeld=True))
+    assert world.player.vy < 0
+    assert world.player.airJumps == constants.maxAirJumps
+    for _ in range(3):
+        world.step(InputCommand(jumpHeld=True))
+    world.step(InputCommand(jump=True, jumpHeld=True))
+    assert world.player.airJumps == 0
+    assert world.player.vy == pytest.approx(constants.doubleJumpVelocity + constants.gravity)
+
+
+def test_jumpBufferFiresOnLanding():
+    world = makeWorld(flatLevel)
+    player = world.player
+    player.airJumps = 0
+    player.coyoteTimer = 0
+    player.onGround = False
+    player.y = 2 * constants.tileSize - player.h - 5.0
+    world.step(InputCommand(jump=True))
+    minVy = 0.0
+    grounded = False
+    for _ in range(14):
+        world.step(InputCommand())
+        grounded = grounded or world.player.onGround
+        minVy = min(minVy, world.player.vy)
+    assert grounded
+    assert minVy == pytest.approx(constants.jumpVelocity + constants.gravity)
+
+
+def test_noBufferNoRejump():
+    world = makeWorld(flatLevel)
+    player = world.player
+    player.airJumps = 0
+    player.coyoteTimer = 0
+    player.onGround = False
+    player.y = 2 * constants.tileSize - player.h - 5.0
+    minVy = 0.0
+    for _ in range(14):
+        world.step(InputCommand())
+        minVy = min(minVy, world.player.vy)
+    assert minVy >= 0.0
+
+
+def test_dashLaunchesAndCoolsDown():
+    world = makeWorld(flatLevel)
+    settle(world, 20)
+    world.step(InputCommand(right=True, dash=True))
+    player = world.player
+    assert player.vx == pytest.approx(constants.dashSpeed)
+    assert player.dashTimer == constants.dashFrames - 1
+    assert player.vy == 0.0
+    assert player.dashCooldown > 0
+
+
+def test_wallSlideClampsFallSpeed():
+    world = makeWorld(wallLevel)
+    player = world.player
+    player.x = 4 * constants.tileSize - player.w
+    player.y = constants.tileSize
+    player.vy = 5.0
+    player.onGround = False
+    world.step(InputCommand(right=True))
+    assert player.wallSliding
+    assert player.vy == pytest.approx(constants.wallSlideSpeed)
+
+
+def test_noWallSlideWhenNotPressingIntoWall():
+    world = makeWorld(wallLevel)
+    player = world.player
+    player.x = 4 * constants.tileSize - player.w
+    player.y = constants.tileSize
+    player.vy = 5.0
+    player.onGround = False
+    world.step(InputCommand(left=True))
+    assert not player.wallSliding
+    assert player.vy > constants.wallSlideSpeed
+
+
+def test_wallJumpPushesAway():
+    world = makeWorld(wallLevel)
+    player = world.player
+    player.x = 4 * constants.tileSize - player.w
+    player.y = constants.tileSize
+    player.vy = 2.0
+    player.onGround = False
+    world.step(InputCommand(right=True, jump=True, jumpHeld=True))
+    assert player.vx == pytest.approx(-constants.wallJumpVelocityX)
+    assert player.vy == pytest.approx(constants.wallJumpVelocityY + constants.gravity)
+
+
+def test_variableJumpCutReducesRise():
+    holdWorld = makeWorld(flatLevel)
+    settle(holdWorld, 20)
+    holdWorld.step(InputCommand(jump=True, jumpHeld=True))
+    holdWorld.step(InputCommand(jumpHeld=True))
+    holdVy = holdWorld.player.vy
+
+    cutWorld = makeWorld(flatLevel)
+    settle(cutWorld, 20)
+    cutWorld.step(InputCommand(jump=True, jumpHeld=True))
+    cutWorld.step(InputCommand(jumpHeld=False))
+    cutVy = cutWorld.player.vy
+
+    assert holdVy < -6.0
+    assert cutVy > -4.0
+    assert cutVy > holdVy