18 files changed, 2036 insertions, 8 deletions

diff --git a/.gitignore b/.gitignore
index 0ca9d1f..cf601f3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,8 +1,7 @@
-*.bmp
 *.o
 CARDS.DLL
 FREECELL.EXE
 SOL.EXE
 config.mk
-dump
-example
+freecell
+sol
diff --git a/Makefile b/Makefile
index 488245d..03bb0ad 100644
--- a/Makefile
+++ b/Makefile
@@ -1,17 +1,26 @@
 CFLAGS += -std=c99 -Wall -Wextra -Wpedantic
+CFLAGS += -Icards
 
 include config.mk
 
-BINS = dump example
+BINS = freecell sol
+OBJS = ${BINS:%=%.o}
 
 all: ${BINS}
 
-${BINS}: cards.o
+${BINS}: cards/cards.o
 
 .o:
-	${CC} ${LDFLAGS} $< cards.o ${LDLIBS} -o $@
+	${CC} ${LDFLAGS} $< cards/cards.o ${LDLIBS} -o $@
 
-cards.o dump.o example.o: cards.h
+${OBJS} cards/cards.o: cards/cards.h
+
+${OBJS}: asset.h stack.h
+
+sol.o: layout.h
+
+cards/cards.h:
+	git submodule update --init
 
 clean:
-	rm -f ${BINS} *.o *.bmp
+	rm -f ${BINS} *.o cards/*.o
diff --git a/asset.h b/asset.h
new file mode 100644
index 0000000..cc37709
--- /dev/null
+++ b/asset.h
@@ -0,0 +1,72 @@
+/* Copyright (C) 2019  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef ASSET_H
+#define ASSET_H
+
+#include <SDL_filesystem.h>
+#include <SDL_rwops.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+struct Paths {
+	char *base;
+	char *pref;
+};
+
+static inline int assetPaths(struct Paths *paths) {
+	paths->base = SDL_GetBasePath();
+	if (!paths->base) return -1;
+	paths->pref = SDL_GetPrefPath("Causal Agency", "Entertainment Pack");
+	if (!paths->pref) return -1;
+	return 0;
+}
+
+static inline SDL_RWops *
+assetOpen(const struct Paths *paths, const char *names[], size_t len) {
+	const char *dirs[3] = { paths->pref, paths->base, "" };
+	for (size_t i = 0; i < 3; ++i) {
+		for (size_t j = 0; j < len; ++j) {
+			char path[1024];
+			snprintf(path, sizeof(path), "%s%s", dirs[i], names[j]);
+			SDL_RWops *rw = SDL_RWFromFile(path, "rb");
+			if (rw) return rw;
+		}
+	}
+	return NULL;
+}
+
+static inline SDL_RWops *assetOpenCards(const struct Paths *paths) {
+	const char *names[3] = { "CARDS.DLL", "SOL.EXE", "cards.dll" };
+	SDL_RWops *rw = assetOpen(paths, names, 3);
+	if (rw) return rw;
+	char msg[4096];
+	snprintf(
+		msg, sizeof(msg), "%s or %s not found in:\n%s\n%s",
+		names[0], names[1], paths->pref, paths->base
+	);
+	SDL_ShowSimpleMessageBox(
+		SDL_MESSAGEBOX_ERROR, "Entertainment Pack", msg, NULL
+	);
+	return NULL;
+}
+
+static inline SDL_RWops *assetOpenFreeCell(const struct Paths *paths) {
+	const char *names[2] = { "FREECELL.EXE", "freecell.exe" };
+	return assetOpen(paths, names, 2);
+}
+
+#endif
diff --git a/cards/.gitignore b/cards/.gitignore
new file mode 100644
index 0000000..0ca9d1f
--- /dev/null
+++ b/cards/.gitignore
@@ -0,0 +1,8 @@
+*.bmp
+*.o
+CARDS.DLL
+FREECELL.EXE
+SOL.EXE
+config.mk
+dump
+example
diff --git a/cards/LICENSE b/cards/LICENSE
new file mode 100644
index 0000000..dba13ed
--- /dev/null
+++ b/cards/LICENSE
@@ -0,0 +1,661 @@
+                    GNU AFFERO GENERAL PUBLIC LICENSE
+                       Version 3, 19 November 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
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+actual knowledge that, but for the patent license, your conveying the
+covered work in a country, or your recipient's use of the covered work
+in a country, would infringe one or more identifiable patents in that
+country that you have reason to believe are valid.
+
+  If, pursuant to or in connection with a single transaction or
+arrangement, you convey, or propagate by procuring conveyance of, a
+covered work, and grant a patent license to some of the parties
+receiving the covered work authorizing them to use, propagate, modify
+or convey a specific copy of the covered work, then the patent license
+you grant is automatically extended to all recipients of the covered
+work and works based on it.
+
+  A patent license is "discriminatory" if it does not include within
+the scope of its coverage, prohibits the exercise of, or is
+conditioned on the non-exercise of one or more of the rights that are
+specifically granted under this License.  You may not convey a covered
+work if you are a party to an arrangement with a third party that is
+in the business of distributing software, under which you make payment
+to the third party based on the extent of your activity of conveying
+the work, and under which the third party grants, to any of the
+parties who would receive the covered work from you, a discriminatory
+patent license (a) in connection with copies of the covered work
+conveyed by you (or copies made from those copies), or (b) primarily
+for and in connection with specific products or compilations that
+contain the covered work, unless you entered into that arrangement,
+or that patent license was granted, prior to 28 March 2007.
+
+  Nothing in this License shall be construed as excluding or limiting
+any implied license or other defenses to infringement that may
+otherwise be available to you under applicable patent law.
+
+  12. No Surrender of Others' Freedom.
+
+  If conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License.  If you cannot convey a
+covered work so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you may
+not convey it at all.  For example, if you agree to terms that obligate you
+to collect a royalty for further conveying from those to whom you convey
+the Program, the only way you could satisfy both those terms and this
+License would be to refrain entirely from conveying the Program.
+
+  13. Remote Network Interaction; Use with the GNU General Public License.
+
+  Notwithstanding any other provision of this License, if you modify the
+Program, your modified version must prominently offer all users
+interacting with it remotely through a computer network (if your version
+supports such interaction) an opportunity to receive the Corresponding
+Source of your version by providing access to the Corresponding Source
+from a network server at no charge, through some standard or customary
+means of facilitating copying of software.  This Corresponding Source
+shall include the Corresponding Source for any work covered by version 3
+of the GNU General Public License that is incorporated pursuant to the
+following paragraph.
+
+  Notwithstanding any other provision of this License, you have
+permission to link or combine any covered work with a work licensed
+under version 3 of the GNU General Public License into a single
+combined work, and to convey the resulting work.  The terms of this
+License will continue to apply to the part which is the covered work,
+but the work with which it is combined will remain governed by version
+3 of the GNU General Public License.
+
+  14. Revised Versions of this License.
+
+  The Free Software Foundation may publish revised and/or new versions of
+the GNU Affero General Public License from time to time.  Such new versions
+will be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+  Each version is given a distinguishing version number.  If the
+Program specifies that a certain numbered version of the GNU Affero General
+Public License "or any later version" applies to it, you have the
+option of following the terms and conditions either of that numbered
+version or of any later version published by the Free Software
+Foundation.  If the Program does not specify a version number of the
+GNU Affero General Public License, you may choose any version ever published
+by the Free Software Foundation.
+
+  If the Program specifies that a proxy can decide which future
+versions of the GNU Affero General Public License can be used, that proxy's
+public statement of acceptance of a version permanently authorizes you
+to choose that version for the Program.
+
+  Later license versions may give you additional or different
+permissions.  However, no additional obligations are imposed on any
+author or copyright holder as a result of your choosing to follow a
+later version.
+
+  15. Disclaimer of Warranty.
+
+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If your software can interact with users remotely through a computer
+network, you should also make sure that it provides a way for users to
+get its source.  For example, if your program is a web application, its
+interface could display a "Source" link that leads users to an archive
+of the code.  There are many ways you could offer source, and different
+solutions will be better for different programs; see section 13 for the
+specific requirements.
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU AGPL, see
+<http://www.gnu.org/licenses/>.
diff --git a/cards/Makefile b/cards/Makefile
new file mode 100644
index 0000000..488245d
--- /dev/null
+++ b/cards/Makefile
@@ -0,0 +1,17 @@
+CFLAGS += -std=c99 -Wall -Wextra -Wpedantic
+
+include config.mk
+
+BINS = dump example
+
+all: ${BINS}
+
+${BINS}: cards.o
+
+.o:
+	${CC} ${LDFLAGS} $< cards.o ${LDLIBS} -o $@
+
+cards.o dump.o example.o: cards.h
+
+clean:
+	rm -f ${BINS} *.o *.bmp
diff --git a/cards.3 b/cards/cards.3
index 26c142c..26c142c 100644
--- a/cards.3
+++ b/cards/cards.3
diff --git a/cards.c b/cards/cards.c
index ddc5b86..ddc5b86 100644
--- a/cards.c
+++ b/cards/cards.c
diff --git a/cards.h b/cards/cards.h
index 9625cb8..9625cb8 100644
--- a/cards.h
+++ b/cards/cards.h
diff --git a/cards/configure b/cards/configure
new file mode 100755
index 0000000..ba1718c
--- /dev/null
+++ b/cards/configure
@@ -0,0 +1,8 @@
+#!/bin/sh
+set -eu
+cflags=$(pkg-config --cflags sdl2)
+ldlibs=$(pkg-config --libs sdl2)
+cat > config.mk << EOF
+CFLAGS += ${cflags}
+LDLIBS += ${ldlibs}
+EOF
diff --git a/dump.1 b/cards/dump.1
index a7fc3db..a7fc3db 100644
--- a/dump.1
+++ b/cards/dump.1
diff --git a/dump.c b/cards/dump.c
index 127d6b1..127d6b1 100644
--- a/dump.c
+++ b/cards/dump.c
diff --git a/example.c b/cards/example.c
index 8790d65..8790d65 100644
--- a/example.c
+++ b/cards/example.c
diff --git a/exefmt.txt b/cards/exefmt.txt
index 51fa9a7..51fa9a7 100644
--- a/exefmt.txt
+++ b/cards/exefmt.txt
diff --git a/freecell.c b/freecell.c
new file mode 100644
index 0000000..3f1ec8d
--- /dev/null
+++ b/freecell.c
@@ -0,0 +1,630 @@
+/* Copyright (C) 2019  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#include <SDL.h>
+#include <cards.h>
+
+#include "asset.h"
+#include "stack.h"
+
+typedef unsigned uint;
+
+enum {
+	Foundation1,
+	Foundation2,
+	Foundation3,
+	Foundation4,
+	Cell1,
+	Cell2,
+	Cell3,
+	Cell4,
+	Tableau1,
+	Tableau2,
+	Tableau3,
+	Tableau4,
+	Tableau5,
+	Tableau6,
+	Tableau7,
+	Tableau8,
+	StacksLen,
+};
+
+static struct Stack stacks[StacksLen];
+
+static uint kingIndex = Cards_KingRight;
+
+struct Move {
+	uint dst;
+	uint src;
+};
+
+enum { QueueLen = 16 };
+static struct {
+	struct Move moves[QueueLen];
+	uint r, w, u;
+} queue;
+
+static void enqueue(uint dst, uint src) {
+	queue.moves[queue.w % QueueLen].dst = dst;
+	queue.moves[queue.w % QueueLen].src = src;
+	queue.w++;
+}
+
+static void dequeue(void) {
+	struct Move move = queue.moves[queue.r++ % QueueLen];
+	push(&stacks[move.dst], pop(&stacks[move.src]));
+	if (move.dst <= Foundation4) {
+		kingIndex = Cards_KingRight;
+	} else if (move.dst <= Cell4) {
+		kingIndex = Cards_KingLeft;
+	}
+}
+
+static bool undo(void) {
+	uint len = queue.w - queue.u;
+	if (!len || len > QueueLen) return false;
+	for (uint i = len - 1; i < len; --i) {
+		struct Move move = queue.moves[(queue.u + i) % QueueLen];
+		push(&stacks[move.src], pop(&stacks[move.dst]));
+	}
+	queue.r = queue.w = queue.u;
+	return true;
+}
+
+static uint lcgState = 1;
+static uint lcgRand(void) {
+	lcgState = (214013 * lcgState + 2531011) % (1 << 31);
+	return lcgState / (1 << 16);
+}
+
+// <https://rosettacode.org/wiki/Deal_cards_for_FreeCell>
+static void deal(uint game) {
+	lcgState = game;
+
+	queue.r = queue.w = queue.u = 0;
+	for (uint i = 0; i < StacksLen; ++i) {
+		clear(&stacks[i]);
+	}
+	kingIndex = Cards_KingRight;
+
+	struct Stack deck = {0};
+	for (Card i = Cards_A; i <= Cards_K; ++i) {
+		push(&deck, Cards_Club + i);
+		push(&deck, Cards_Diamond + i);
+		push(&deck, Cards_Heart + i);
+		push(&deck, Cards_Spade + i);
+	}
+
+	uint stack = 0;
+	while (deck.len) {
+		uint i = lcgRand() % deck.len;
+		Card card = deck.cards[i];
+		deck.cards[i] = deck.cards[--deck.len];
+		push(&stacks[Tableau1 + stack++ % 8], card);
+	}
+}
+
+static bool win(void) {
+	for (uint i = Foundation1; i <= Foundation4; ++i) {
+		if (stacks[i].len != 13) return false;
+	}
+	return true;
+}
+
+static bool valid(uint dst, Card card) {
+	Card top = peek(&stacks[dst]);
+	if (dst <= Foundation4) {
+		if (!top) return rank(card) == Cards_A;
+		return suit(card) == suit(top)
+			&& rank(card) == rank(top) + 1;
+	}
+	if (!top) return true;
+	if (dst >= Tableau1) {
+		return color(card) != color(top)
+			&& rank(card) == rank(top) - 1;
+	}
+	return false;
+}
+
+static void autoEnqueue(void) {
+	Card min[] = { Cards_K, Cards_K };
+	for (uint i = Cell1; i <= Tableau8; ++i) {
+		for (uint j = 0; j < stacks[i].len; ++j) {
+			Card card = stacks[i].cards[j];
+			if (rank(card) < min[color(card)]) {
+				min[color(card)] = rank(card);
+			}
+		}
+	}
+
+	for (uint src = Cell1; src <= Tableau8; ++src) {
+		Card card = peek(&stacks[src]);
+		if (!card) continue;
+		if (rank(card) > Cards_2) {
+			if (min[!color(card)] < rank(card)) continue;
+		}
+		for (uint dst = Foundation1; dst <= Foundation4; ++dst) {
+			if (valid(dst, card)) {
+				enqueue(dst, src);
+				return;
+			}
+		}
+	}
+}
+
+static void moveSingle(uint dst, uint src) {
+	if (valid(dst, peek(&stacks[src]))) {
+		queue.u = queue.w;
+		enqueue(dst, src);
+	}
+}
+
+static uint moveDepth(uint src) {
+	struct Stack stack = stacks[src];
+	if (stack.len < 2) return stack.len;
+	uint n = 1;
+	for (uint i = stack.len - 2; i < stack.len; --i, ++n) {
+		if (color(stack.cards[i]) == color(stack.cards[i + 1])) break;
+		if (rank(stack.cards[i]) != rank(stack.cards[i + 1]) + 1) break;
+	}
+	return n;
+}
+
+static uint freeCells(uint cells[], uint dst) {
+	uint len = 0;
+	for (uint i = Cell1; i <= Tableau8; ++i) {
+		if (i == dst) continue;
+		if (!stacks[i].len) cells[len++] = i;
+	}
+	return len;
+}
+
+static void moveColumn(uint dst, uint src) {
+	uint cells[StacksLen];
+	uint free = freeCells(cells, dst);
+
+	uint depth;
+	for (depth = moveDepth(src); depth; --depth) {
+		if (free < depth - 1) continue;
+		if (valid(dst, stacks[src].cards[stacks[src].len - depth])) break;
+	}
+	if (depth < 2 || dst <= Cell4) {
+		moveSingle(dst, src);
+		return;
+	}
+
+	queue.u = queue.w;
+	for (uint i = 0; i < depth - 1; ++i) {
+		enqueue(cells[i], src);
+	}
+	enqueue(dst, src);
+	for (uint i = depth - 2; i < depth - 1; --i) {
+		enqueue(dst, cells[i]);
+	}
+}
+
+enum {
+	CardWidth = Cards_CardWidth,
+	CardHeight = Cards_CardHeight,
+
+	CellX = 0,
+	CellY = 0,
+
+	KingMarginX = 13,
+	KingX = CellX + 4 * CardWidth + KingMarginX,
+	KingY = 18,
+	KingPadX = 3,
+	KingPadY = 3,
+	KingWidth = Cards_KingWidth + 2 * KingPadX,
+	KingHeight = Cards_KingHeight + 2 * KingPadY,
+
+	FoundationX = KingX + KingWidth + KingMarginX,
+	FoundationY = CellY,
+
+	StackMarginX = 7,
+	StackMarginY = 10,
+	StackDeltaY = 17,
+
+	TableauX = StackMarginX,
+	TableauY = CellY + CardHeight + StackMarginY,
+
+	KingWinMarginX = 10,
+	KingWinMarginY = 10,
+	KingWinX = KingWinMarginX,
+	KingWinY = CellY + CardHeight + KingWinMarginY,
+	KingWinWidth = 320,
+	KingWinHeight = 320,
+
+	WindowWidth = 8 * CardWidth + 9 * StackMarginX + 1,
+	WindowHeight = KingWinY + KingWinHeight + KingWinMarginY,
+};
+
+static struct SDL_Rect rects[StacksLen];
+
+static void initRects(void) {
+	SDL_Rect rect = { CellX, CellY, CardWidth, CardHeight };
+	for (uint i = Cell1; i <= Cell4; ++i) {
+		rects[i] = rect;
+		rect.x += CardWidth;
+	}
+
+	rect.x = FoundationX;
+	rect.y = FoundationY;
+	for (uint i = Foundation1; i <= Foundation4; ++i) {
+		rects[i] = rect;
+		rect.x += CardWidth;
+	}
+
+	rect.x = TableauX;
+	rect.y = TableauY;
+	rect.h = WindowHeight - TableauY;
+	for (uint i = Tableau1; i <= Tableau8; ++i) {
+		rects[i] = rect;
+		rect.x += CardWidth + StackMarginX;
+	}
+}
+
+static uint pointStack(SDL_Point point) {
+	uint i;
+	for (i = 0; i < StacksLen; ++i) {
+		if (SDL_PointInRect(&point, &rects[i])) break;
+	}
+	return i;
+}
+
+static SDL_Window *window;
+
+static void err(const char *title) {
+	int error = SDL_ShowSimpleMessageBox(
+		SDL_MESSAGEBOX_ERROR, title, SDL_GetError(), window
+	);
+	if (error) fprintf(stderr, "%s\n", SDL_GetError());
+	exit(EXIT_FAILURE);
+}
+
+static bool playAgain(void) {
+	SDL_MessageBoxButtonData buttons[] = {
+		{ SDL_MESSAGEBOX_BUTTON_RETURNKEY_DEFAULT, true, "Yes" },
+		{ SDL_MESSAGEBOX_BUTTON_ESCAPEKEY_DEFAULT, false, "No" },
+	};
+	SDL_MessageBoxData data = {
+		.window = window,
+		.title = "Game Over",
+		.message = "Congratulations, you win!\n\nDo you want to play again?",
+		.buttons = buttons,
+		.numbuttons = SDL_arraysize(buttons),
+	};
+	int choice;
+	if (SDL_ShowMessageBox(&data, &choice) < 0) err("SDL_ShowMessageBox");
+	return choice;
+}
+
+enum Choice {
+	Cancel,
+	Column,
+	Single,
+};
+
+static enum Choice chooseMove(void) {
+	SDL_MessageBoxButtonData buttons[] = {
+		{ SDL_MESSAGEBOX_BUTTON_RETURNKEY_DEFAULT, Column, "Move column" },
+		{ 0, Single, "Move single card" },
+		{ SDL_MESSAGEBOX_BUTTON_ESCAPEKEY_DEFAULT, Cancel, "Cancel" },
+	};
+	SDL_MessageBoxData data = {
+		.window = window,
+		.title = "Move to Empty Column...",
+		.message = "",
+		.buttons = buttons,
+		.numbuttons = SDL_arraysize(buttons),
+	};
+	int choice;
+	if (SDL_ShowMessageBox(&data, &choice) < 0) err("SDL_ShowMessageBox");
+	return choice;
+}
+
+static void newGame(void) {
+	uint game = 1 + randUniform(32000);
+	deal(game);
+	char buf[sizeof("FreeCell Game #32000")];
+	snprintf(buf, sizeof(buf), "FreeCell Game #%u", game);
+	SDL_SetWindowTitle(window, buf);
+}
+
+static Card hiliteRank;
+static SDL_Point revealPoint;
+static uint fromStack = StacksLen;
+
+static bool keyDown(SDL_KeyboardEvent key) {
+	switch (key.keysym.sym) {
+		case SDLK_F2: newGame(); return true;
+		case SDLK_BACKSPACE: return undo();
+	}
+	if (key.repeat) return false;
+	switch (key.keysym.sym) {
+		break; case SDLK_a: hiliteRank = Cards_A;
+		break; case SDLK_2: hiliteRank = Cards_2;
+		break; case SDLK_3: hiliteRank = Cards_3;
+		break; case SDLK_4: hiliteRank = Cards_4;
+		break; case SDLK_5: hiliteRank = Cards_5;
+		break; case SDLK_6: hiliteRank = Cards_6;
+		break; case SDLK_7: hiliteRank = Cards_7;
+		break; case SDLK_8: hiliteRank = Cards_8;
+		break; case SDLK_9: hiliteRank = Cards_9;
+		break; case SDLK_1: hiliteRank = Cards_10;
+		break; case SDLK_0: hiliteRank = Cards_10;
+		break; case SDLK_j: hiliteRank = Cards_J;
+		break; case SDLK_q: hiliteRank = Cards_Q;
+		break; case SDLK_k: hiliteRank = Cards_K;
+		break; default: return false;
+	}
+	return true;
+}
+
+static bool keyUp(SDL_KeyboardEvent key) {
+	(void)key;
+	if (hiliteRank) {
+		hiliteRank = 0;
+		return true;
+	}
+	return false;
+}
+
+static bool mouseButtonDown(SDL_MouseButtonEvent button) {
+	if (button.button == SDL_BUTTON_RIGHT) {
+		revealPoint.x = button.x;
+		revealPoint.y = button.y;
+		return true;
+	}
+	return false;
+}
+
+static bool mouseButtonUp(SDL_MouseButtonEvent button) {
+	if (win() && playAgain()) {
+		newGame();
+		return true;
+	}
+
+	if (button.button == SDL_BUTTON_RIGHT && revealPoint.x) {
+		revealPoint.x = 0;
+		revealPoint.y = 0;
+		return true;
+	}
+
+	SDL_Point point = { button.x, button.y };
+	uint stack = pointStack(point);
+	if (button.clicks % 2 == 0) {
+		for (stack = Cell1; stack <= Cell4; ++stack) {
+			if (!stacks[stack].len) break;
+		}
+	}
+
+	if (fromStack < StacksLen && stack < StacksLen) {
+		if (moveDepth(fromStack) > 1 && stack > Cell4 && !stacks[stack].len) {
+			switch (chooseMove()) {
+				break; case Single: moveSingle(stack, fromStack);
+				break; case Column: moveColumn(stack, fromStack);
+				break; case Cancel: break;
+			}
+		} else {
+			moveColumn(stack, fromStack);
+		}
+	}
+
+	if (fromStack < StacksLen) {
+		fromStack = StacksLen;
+		return true;
+	}
+	if (stack < StacksLen && stack > Foundation4 && stacks[stack].len) {
+		fromStack = stack;
+		return true;
+	}
+
+	return false;
+}
+
+static SDL_Renderer *render;
+static struct {
+	SDL_Texture *cards[Cards_Empty];
+	SDL_Texture *hilites[Cards_Empty];
+	SDL_Texture *kings[Cards_FreeCellCount];
+} tex;
+
+static void renderOutline(SDL_Rect rect, bool out) {
+	int right = rect.x + rect.w - 1;
+	int bottom = rect.y + rect.h - 1;
+	SDL_Point topLeft[3] = {
+		{ rect.x, bottom - 1 },
+		{ rect.x, rect.y },
+		{ right - 1, rect.y },
+	};
+	SDL_Point bottomRight[3] = {
+		{ rect.x + 1, bottom },
+		{ right, bottom },
+		{ right, rect.y + 1 },
+	};
+	SDL_SetRenderDrawColor(render, 0x00, 0x00, 0x00, 0xFF);
+	SDL_RenderDrawLines(render, out ? bottomRight : topLeft, 3);
+	SDL_SetRenderDrawColor(render, 0x00, 0xFF, 0x00, 0xFF);
+	SDL_RenderDrawLines(render, out ? topLeft : bottomRight, 3);
+}
+
+static void renderOutlines(void) {
+	for (uint i = Foundation1; i <= Cell4; ++i) {
+		renderOutline(rects[i], false);
+	}
+}
+
+static void renderKing(void) {
+	SDL_Rect box = { KingX, KingY, KingWidth, KingHeight };
+	renderOutline(box, true);
+	if (win()) {
+		SDL_Rect king = { KingWinX, KingWinY, KingWinWidth, KingWinHeight };
+		SDL_RenderCopy(render, tex.kings[Cards_KingWin], NULL, &king);
+	} else {
+		SDL_Rect king = {
+			KingX + KingPadX, KingY + KingPadY,
+			Cards_KingWidth, Cards_KingHeight,
+		};
+		SDL_RenderCopy(render, tex.kings[kingIndex], NULL, &king);
+	}
+}
+
+static void renderCard(SDL_Rect rect, Card card, bool hilite) {
+	SDL_Texture *texture = (hilite ? tex.hilites : tex.cards)[card];
+	SDL_RenderCopy(render, texture, NULL, &rect);
+}
+
+static void renderStack(uint stack) {
+	Card revealCard = 0;
+	SDL_Rect revealRect = {0};
+	SDL_Rect rect = { rects[stack].x, rects[stack].y, CardWidth, CardHeight };
+	for (uint i = 0; i < stacks[stack].len; ++i) {
+		Card card = stacks[stack].cards[i];
+		if (SDL_PointInRect(&revealPoint, &rect)) {
+			revealCard = card;
+			revealRect = rect;
+		}
+		bool hilite = (stack == fromStack && i == stacks[stack].len - 1);
+		renderCard(rect, card, hilite || rank(card) == hiliteRank);
+		rect.y += StackDeltaY;
+	}
+	if (revealCard) {
+		renderCard(revealRect, revealCard, false);
+	}
+}
+
+static void renderStacks(void) {
+	for (uint i = Foundation1; i <= Cell4; ++i) {
+		Card card = peek(&stacks[i]);
+		if (!card) continue;
+		bool hilite = (i == fromStack || rank(card) == hiliteRank);
+		renderCard(rects[i], card, hilite);
+	}
+	for (uint i = Tableau1; i <= Tableau8; ++i) {
+		renderStack(i);
+	}
+}
+
+int main(void) {
+	int error;
+
+	if (SDL_Init(SDL_INIT_VIDEO) < 0) err("SDL_Init");
+	atexit(SDL_Quit);
+
+	struct Paths paths;
+	if (assetPaths(&paths) < 0) err("SDL_GetPrefPath");
+
+	bool haveFreeCell = false;
+	struct {
+		SDL_Surface *cards[Cards_Empty];
+		SDL_Surface *freeCell[Cards_FreeCellCount];
+	} res;
+
+	SDL_RWops *rw = assetOpenCards(&paths);
+	if (!rw) return EXIT_FAILURE;
+	error = Cards_LoadCards(
+		res.cards, Cards_Empty, rw,
+		Cards_AlphaCorners | Cards_BlackBorders
+	);
+	if (error) err("Cards_LoadCards");
+	SDL_RWclose(rw);
+
+	rw = assetOpenFreeCell(&paths);
+	if (rw) {
+		haveFreeCell = true;
+		error = Cards_LoadFreeCell(
+			res.freeCell, Cards_FreeCellCount, rw,
+			Cards_ColorKey
+		);
+		if (error) err("Cards_LoadFreeCell");
+		SDL_RWclose(rw);
+	}
+
+	error = SDL_CreateWindowAndRenderer(
+		WindowWidth, WindowHeight, SDL_WINDOW_ALLOW_HIGHDPI,
+		&window, &render
+	);
+	if (error) err("SDL_CreateWindowAndRenderer");
+	SDL_SetWindowTitle(window, "FreeCell");
+
+	SDL_RenderSetIntegerScale(render, SDL_TRUE);
+	SDL_RenderSetLogicalSize(render, WindowWidth, WindowHeight);
+
+	for (uint i = 0; i < Cards_Empty; ++i) {
+		if (!res.cards[i]) continue;
+
+		tex.cards[i] = SDL_CreateTextureFromSurface(render, res.cards[i]);
+		if (!tex.cards[i]) err("SDL_CreateTextureFromSurface");
+
+		if (Cards_InvertSurface(res.cards[i]) < 0) err("Cards_hilitesurface");
+		tex.hilites[i] = SDL_CreateTextureFromSurface(render, res.cards[i]);
+		if (!tex.hilites[i]) err("SDL_CreateTextureFromSurface");
+
+		SDL_FreeSurface(res.cards[i]);
+	}
+
+	if (haveFreeCell) {
+		for (uint i = 0; i < Cards_FreeCellCount; ++i) {
+			if (!res.freeCell[i]) continue;
+			tex.kings[i] = SDL_CreateTextureFromSurface(render, res.freeCell[i]);
+			if (!tex.kings[i]) err("SDL_CreateTextureFromSurface");
+			SDL_FreeSurface(res.freeCell[i]);
+		}
+	}
+
+	srand(time(NULL));
+	newGame();
+	
+	initRects();
+	for (;;) {
+		SDL_SetRenderDrawColor(render, 0x00, 0xAA, 0x55, 0xFF);
+		SDL_RenderClear(render);
+		renderOutlines();
+		renderStacks();
+		if (haveFreeCell) renderKing();
+		SDL_RenderPresent(render);
+
+		if (queue.r < queue.w) {
+			dequeue();
+			if (queue.r == queue.w) autoEnqueue();
+			if (queue.r < queue.w) SDL_Delay(50);
+			continue;
+		}
+
+		bool update = false;
+		while (!update) {
+			SDL_Event event;
+			SDL_WaitEvent(&event);
+			switch (event.type) {
+				break; case SDL_QUIT: return EXIT_SUCCESS;
+				break; case SDL_KEYDOWN: update = keyDown(event.key);
+				break; case SDL_KEYUP: update = keyUp(event.key);
+				break; case SDL_MOUSEBUTTONDOWN: {
+					update = mouseButtonDown(event.button);
+				}
+				break; case SDL_MOUSEBUTTONUP: {
+					update = mouseButtonUp(event.button);
+				}
+			}
+		}
+	}
+}
diff --git a/layout.h b/layout.h
new file mode 100644
index 0000000..cbff6df
--- /dev/null
+++ b/layout.h
@@ -0,0 +1,110 @@
+/* Copyright (C) 2019  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef LAYOUT_H
+#define LAYOUT_H
+
+#include <SDL_rect.h>
+#include <assert.h>
+
+#include "stack.h"
+
+#ifndef LAYOUT_CAP
+#define LAYOUT_CAP 64
+#endif
+
+typedef unsigned uint;
+
+struct Item {
+	SDL_Rect rect;
+	Card card;
+};
+
+struct List {
+	uint len;
+	struct Item items[LAYOUT_CAP];
+};
+
+static inline void listClear(struct List *list) {
+	list->len = 0;
+}
+
+static inline void
+listPush(struct List *list, const struct SDL_Rect *rect, Card card) {
+	assert(list->len < LAYOUT_CAP);
+	struct Item item = { *rect, card };
+	list->items[list->len++] = item;
+}
+
+static inline struct Item *listFind(struct List *list, const SDL_Point *point) {
+	for (uint i = list->len - 1; i < list->len; --i) {
+		if (SDL_PointInRect(point, &list->items[i].rect)) {
+			return &list->items[i];
+		}
+	}
+	return NULL;
+}
+
+struct Layout {
+	struct List main;
+	struct List drag;
+	struct Item dragItem;
+};
+
+static inline void layoutClear(struct Layout *layout) {
+	listClear(&layout->main);
+	listClear(&layout->drag);
+}
+
+struct Style {
+	uint increment;
+	int deltaXBack;
+	int deltaYBack;
+	int deltaXFront;
+	int deltaYFront;
+};
+
+enum {
+	SquareIncrement = 24 / 3,
+	SquareDeltaX = 2,
+	SquareDeltaY = 1,
+};
+static const struct Style Flat = { 1, 0, 0, 0, 0 };
+static const struct Style Square = {
+	SquareIncrement, SquareDeltaX, SquareDeltaY, SquareDeltaX, SquareDeltaY,
+};
+
+static inline void
+layoutStack(
+	struct Layout *layout, SDL_Rect *rect,
+	const struct Stack *stack, const struct Style *style
+) {
+	struct List *list = &layout->main;
+	for (uint i = 0; i < stack->len; ++i) {
+		Card card = stack->cards[i];
+		if (card == layout->dragItem.card) {
+			list = &layout->drag;
+			*rect = layout->dragItem.rect;
+		}
+		listPush(list, rect, card);
+		if ((i + 1) % style->increment == 0) {
+			rect->x += (card > 0 ? style->deltaXFront : style->deltaXBack);
+			rect->y += (card > 0 ? style->deltaYFront : style->deltaYBack);
+		}
+	}
+}
+
+#endif
diff --git a/sol.c b/sol.c
new file mode 100644
index 0000000..5622395
--- /dev/null
+++ b/sol.c
@@ -0,0 +1,392 @@
+/* Copyright (C) 2019  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#include <SDL.h>
+#include <cards.h>
+
+#include "asset.h"
+#include "layout.h"
+#include "stack.h"
+
+#define ARRAY_LEN(a) (sizeof(a) / sizeof((a)[0]))
+
+enum {
+	Stock,
+	Waste1,
+	Waste3,
+	Foundation1,
+	Foundation2,
+	Foundation3,
+	Foundation4,
+	Tableau1,
+	Tableau2,
+	Tableau3,
+	Tableau4,
+	Tableau5,
+	Tableau6,
+	Tableau7,
+	StacksLen,
+};
+
+static struct Stack stacks[StacksLen];
+
+// TODO: Scoring method, score, time.
+static struct {
+	uint draw;
+} game = {
+	.draw = 3,
+};
+
+typedef void StackFn(struct Stack *dst, struct Stack *src, Uint8 len);
+
+static struct {
+	StackFn *fn;
+	uint dst;
+	uint src;
+	uint len;
+} undo;
+
+static void gameDo(StackFn *fn, uint dst, uint src, uint len) {
+	undo.fn = fn;
+	undo.dst = src;
+	undo.src = dst;
+	undo.len = len;
+	fn(&stacks[dst], &stacks[src], len);
+}
+
+static bool gameUndo(void) {
+	if (!undo.fn) return false;
+	undo.fn(&stacks[undo.dst], &stacks[undo.src], undo.len);
+	undo.fn = NULL;
+	return true;
+}
+
+static void gameDeal(void) {
+	undo.fn = NULL;
+	for (uint i = 0; i < StacksLen; ++i) {
+		clear(&stacks[i]);
+	}
+	stacks[Stock] = Deck;
+	shuffle(&stacks[Stock]);
+	for (uint i = Tableau1; i <= Tableau7; ++i) {
+		moveTo(&stacks[i], &stacks[Stock], i - Tableau1);
+		flipTo(&stacks[i], &stacks[Stock], 1);
+	}
+}
+
+static void gameDraw(void) {
+	moveTo(&stacks[Waste1], &stacks[Waste3], stacks[Waste3].len);
+	if (stacks[Stock].len) {
+		if (game.draw > 1) {
+			gameDo(flipTo, Waste3, Stock, game.draw);
+		} else {
+			gameDo(flipTo, Waste1, Stock, 1);
+		}
+	} else {
+		gameDo(flipTo, Stock, Waste1, stacks[Waste1].len);
+	}
+}
+
+static bool gameFind(uint *stack, uint *index, Card card) {
+	for (*stack = 0; *stack < StacksLen; ++*stack) {
+		for (*index = 0; *index < stacks[*stack].len; ++*index) {
+			if (stacks[*stack].cards[*index] == card) return true;
+		}
+	}
+	return false;
+}
+
+static bool gameAvail(Card card) {
+	uint stack, index;
+	if (card < 0) return false;
+	if (!gameFind(&stack, &index, card)) return false;
+
+	bool top = (card == peek(&stacks[stack]));
+	if (stack == Waste1) {
+		return top && !stacks[Waste3].len;
+	} else if (stack == Waste3) {
+		return top;
+	} else if (stack >= Foundation1 && stack <= Foundation4) {
+		return top;
+	} else if (stack >= Tableau1 && stack <= Tableau7) {
+		return true;
+	} else {
+		return false;
+	}
+}
+
+static bool gameReveal(Card card) {
+	uint stack, index;
+	if (!gameFind(&stack, &index, card)) return false;
+	if (stack < Tableau1 || stack > Tableau7) return false;
+	if (card != peek(&stacks[stack])) return false;
+	if (card > 0) return false;
+	gameDo(flipTo, stack, stack, 1);
+	return true;
+}
+
+static bool gameMove(uint dest, Card card) {
+	uint source, index;
+	if (!gameFind(&source, &index, card)) return false;
+	if (source == dest) return false;
+
+	uint count = stacks[source].len - index;
+	Card destTop = peek(&stacks[dest]);
+
+	if (dest >= Foundation1 && dest <= Foundation4) {
+		if (count > 1) return false;
+		if (!destTop && rank(card) != Cards_A) return false;
+		if (destTop && suit(card) != suit(destTop)) return false;
+		if (destTop && rank(card) != rank(destTop) + 1) return false;
+		gameDo(moveTo, dest, source, 1);
+		return true;
+	}
+
+	if (dest >= Tableau1 && dest <= Tableau7) {
+		if (!destTop && rank(card) != Cards_K) return false;
+		if (destTop && color(card) == color(destTop)) return false;
+		if (destTop && rank(card) != rank(destTop) - 1) return false;
+		gameDo(moveTo, dest, source, count);
+		return true;
+	}
+
+	return false;
+}
+
+enum {
+	CardWidth = Cards_CardWidth,
+	CardHeight = Cards_CardHeight,
+
+	StackMarginX = 11,
+	StackMarginY = 6,
+
+	StockX = StackMarginX,
+	StockY = StackMarginY,
+
+	WasteX = StockX + CardWidth + StackMarginX,
+	WasteY = StackMarginY,
+
+	FoundationX = WasteX + 2 * (CardWidth + StackMarginX),
+	FoundationY = StackMarginY,
+
+	TableauX = StackMarginX,
+	TableauY = StockY + CardHeight + StackMarginY,
+
+	FanRightDeltaX = 14,
+	FanDownDeltaYBack = 3,
+	FanDownDeltaYFront = 15,
+
+	WindowWidth = 7 * CardWidth + 8 * StackMarginX,
+	WindowHeight = 2 * (StackMarginY + CardHeight)
+		+ 6 * FanDownDeltaYBack
+		+ 12 * FanDownDeltaYFront
+		+ StackMarginY,
+};
+
+static const struct Style FanRight = {
+	1, 0, 0, FanRightDeltaX, SquareDeltaY
+};
+static const struct Style FanDown = {
+	1, 0, FanDownDeltaYBack, 0, FanDownDeltaYFront
+};
+
+static struct SDL_Rect stackRects[StacksLen];
+static struct Layout layout;
+static uint backTexture = Cards_Back1;
+
+static void updateLayout(void) {
+	layoutClear(&layout);
+
+	SDL_Rect stock = { StockX, StockY, CardWidth, CardHeight };
+	stackRects[Stock] = stock;
+	listPush(&layout.main, &stock, Cards_O);
+	layoutStack(&layout, &stock, &stacks[Stock], &Square);
+
+	SDL_Rect waste = { WasteX, WasteY, CardWidth, CardHeight };
+	layoutStack(&layout, &waste, &stacks[Waste1], &Square);
+	layoutStack(&layout, &waste, &stacks[Waste3], &FanRight);
+
+	SDL_Rect found = { FoundationX, FoundationY, CardWidth, CardHeight };
+	for (uint i = Foundation1; i <= Foundation4; ++i) {
+		stackRects[i] = found;
+		listPush(&layout.main, &found, Cards_Empty);
+		SDL_Rect rect = found;
+		layoutStack(&layout, &rect, &stacks[i], &Square);
+		found.x += CardWidth + StackMarginX;
+	}
+
+	SDL_Rect table = { TableauX, TableauY, CardWidth, CardHeight };
+	for (uint i = Tableau1; i <= Tableau7; ++i) {
+		stackRects[i] = table;
+		stackRects[i].h = WindowHeight;
+		SDL_Rect rect = table;
+		layoutStack(&layout, &rect, &stacks[i], &FanDown);
+		table.x += CardWidth + StackMarginX;
+	}
+}
+
+static bool keyDown(SDL_KeyboardEvent key) {
+	switch (key.keysym.sym) {
+		case SDLK_F2: gameDeal(); return true;
+		case SDLK_BACKSPACE: return gameUndo();
+		case SDLK_b: {
+			backTexture -= Cards_Back1;
+			backTexture += 1;
+			backTexture %= 12;
+			backTexture += Cards_Back1;
+			return true;
+		}
+		case SDLK_d: {
+			game.draw = (game.draw == 1 ? 3 : 1);
+			gameDeal();
+			return true;
+		}
+		default: return false;
+	}
+}
+
+static bool mouseButtonDown(SDL_MouseButtonEvent button) {
+	struct SDL_Point point = { button.x, button.y };
+	if (SDL_PointInRect(&point, &stackRects[Stock])) {
+		gameDraw();
+		return true;
+	}
+	struct Item *item = listFind(&layout.main, &point);
+	if (!item) return false;
+	if (!gameAvail(item->card)) return gameReveal(item->card);
+	if (button.clicks % 2 == 0) {
+		for (uint dest = Foundation1; dest <= Foundation4; ++dest) {
+			if (gameMove(dest, item->card)) return true;
+		}
+		return false;
+	}
+	layout.dragItem = *item;
+	return true;
+}
+
+static bool mouseButtonUp(SDL_MouseButtonEvent button) {
+	(void)button;
+	if (!layout.dragItem.card) return false;
+	for (uint dest = 0; dest < StacksLen; ++dest) {
+		if (SDL_HasIntersection(&layout.dragItem.rect, &stackRects[dest])) {
+			if (gameMove(dest, layout.dragItem.card)) break;
+		}
+	}
+	layout.dragItem.card = 0;
+	return true;
+}
+
+static bool mouseMotion(SDL_MouseMotionEvent motion) {
+	if (!motion.state) return false;
+	layout.dragItem.rect.x += motion.xrel;
+	layout.dragItem.rect.y += motion.yrel;
+	return true;
+}
+
+static SDL_Renderer *render;
+static SDL_Texture *textures[Cards_CardCount];
+
+static void renderList(const struct List *list) {
+	for (uint i = 0; i < list->len; ++i) {
+		int tex = list->items[i].card;
+		if (tex < 0) tex = backTexture;
+		SDL_RenderCopy(render, textures[tex], NULL, &list->items[i].rect);
+	}
+}
+
+static void err(const char *title) {
+	int error = SDL_ShowSimpleMessageBox(
+		SDL_MESSAGEBOX_ERROR, title, SDL_GetError(), NULL
+	);
+	if (error) fprintf(stderr, "%s\n", SDL_GetError());
+	exit(EXIT_FAILURE);
+}
+
+int main(void) {
+	if (SDL_Init(SDL_INIT_VIDEO) < 0) err("SDL_Init");
+	atexit(SDL_Quit);
+
+	struct Paths paths;
+	if (assetPaths(&paths) < 0) err("SDL_GetPrefPath");
+
+	SDL_RWops *rw = assetOpenCards(&paths);
+	if (!rw) return EXIT_FAILURE;
+
+	SDL_Surface *surfaces[Cards_CardCount];
+	int error = Cards_LoadCards(
+		surfaces, Cards_CardCount,
+		rw, Cards_ColorKey | Cards_AlphaCorners | Cards_BlackBorders
+	);
+	if (error) err("Cards_LoadCards");
+	SDL_RWclose(rw);
+
+	SDL_Window *window;
+	error = SDL_CreateWindowAndRenderer(
+		WindowWidth, WindowHeight, SDL_WINDOW_ALLOW_HIGHDPI,
+		&window, &render
+	);
+	if (error) err("SDL_CreateWindowAndRenderer");
+	SDL_SetWindowTitle(window, "Solitaire");
+
+	SDL_RenderSetIntegerScale(render, SDL_TRUE);
+	SDL_RenderSetLogicalSize(render, WindowWidth, WindowHeight);
+
+	for (uint i = 0; i < Cards_CardCount; ++i) {
+		textures[i] = NULL;
+		if (!surfaces[i]) continue;
+		textures[i] = SDL_CreateTextureFromSurface(render, surfaces[i]);
+		if (!textures[i]) err("SDL_CreateTextureFromSurface");
+		SDL_FreeSurface(surfaces[i]);
+	}
+
+	srand(time(NULL));
+	backTexture = Cards_Back1 + randUniform(12);
+	gameDeal();
+
+	for (;;) {
+		updateLayout();
+
+		SDL_SetRenderDrawColor(render, 0x00, 0xAA, 0x55, 0xFF);
+		SDL_RenderClear(render);
+		renderList(&layout.main);
+		renderList(&layout.drag);
+		SDL_RenderPresent(render);
+
+		SDL_Event event;
+		for (;;) {
+			SDL_WaitEvent(&event);
+			if (event.type == SDL_QUIT) {
+				goto quit;
+			} else if (event.type == SDL_KEYDOWN) {
+				if (keyDown(event.key)) break;
+			} else if (event.type == SDL_MOUSEBUTTONDOWN) {
+				if (mouseButtonDown(event.button)) break;
+			} else if (event.type == SDL_MOUSEBUTTONUP) {
+				if (mouseButtonUp(event.button)) break;
+			} else if (event.type == SDL_MOUSEMOTION) {
+				if (mouseMotion(event.motion)) break;
+			}
+		}
+	}
+
+quit:
+	SDL_Quit();
+}
diff --git a/stack.h b/stack.h
new file mode 100644
index 0000000..c315729
--- /dev/null
+++ b/stack.h
@@ -0,0 +1,122 @@
+/* Copyright (C) 2019  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef STACK_H
+#define STACK_H
+
+#include <assert.h>
+#include <stdlib.h>
+
+#include <SDL_stdinc.h>
+#include <cards.h>
+
+#ifndef STACK_CAP
+#define STACK_CAP 52
+#endif
+
+#if STACK_CAP < 52
+#error "Stack capacity too small for deck"
+#endif
+
+typedef Sint8 Card;
+
+static inline int suit(Card card) {
+	card = abs(card);
+	if (card > Cards_Spade) {
+		return Cards_Spade;
+	} else if (card > Cards_Heart) {
+		return Cards_Heart;
+	} else if (card > Cards_Diamond) {
+		return Cards_Diamond;
+	} else {
+		return Cards_Club;
+	}
+}
+
+static inline int color(Card card) {
+	return suit(card) == Cards_Diamond || suit(card) == Cards_Heart;
+}
+
+static inline int rank(Card card) {
+	return abs(card) - suit(card);
+}
+
+struct Stack {
+	Uint8 len;
+	Card cards[STACK_CAP];
+};
+
+static const struct Stack Deck = {
+	.len = 52,
+	.cards = {
+		-1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13,
+		-14, -15, -16, -17, -18, -19, -20, -21, -22, -23, -24, -25, -26,
+		-27, -28, -29, -30, -31, -32, -33, -34, -35, -36, -37, -38, -39,
+		-40, -41, -42, -43, -44, -45, -46, -47, -48, -49, -50, -51, -52,
+	},
+};
+
+static inline void clear(struct Stack *stack) {
+	stack->len = 0;
+}
+
+static inline void push(struct Stack *stack, Card card) {
+	assert(stack->len < STACK_CAP);
+	stack->cards[stack->len++] = card;
+}
+
+static inline Card pop(struct Stack *stack) {
+	if (!stack->len) return 0;
+	return stack->cards[--stack->len];
+}
+
+static inline Card peek(const struct Stack *stack) {
+	if (!stack->len) return 0;
+	return stack->cards[stack->len - 1];
+}
+
+static inline void flipTo(struct Stack *dst, struct Stack *src, Uint8 n) {
+	if (n > src->len) n = src->len;
+	for (Uint8 i = 0; i < n; ++i) {
+		push(dst, -pop(src));
+	}
+}
+
+static inline void moveTo(struct Stack *dst, struct Stack *src, Uint8 n) {
+	if (n > src->len) n = src->len;
+	for (Uint8 i = 0; i < n; ++i) {
+		push(dst, src->cards[src->len - n + i]);
+	}
+	src->len -= n;
+}
+
+static inline int randUniform(int bound) {
+	for (;;) {
+		int r = rand();
+		if (r >= RAND_MAX % bound) return r % bound;
+	}
+}
+
+static inline void shuffle(struct Stack *stack) {
+	for (Uint8 i = stack->len - 1; i > 0; --i) {
+		Uint8 j = randUniform(i + 1);
+		Card x = stack->cards[i];
+		stack->cards[i] = stack->cards[j];
+		stack->cards[j] = x;
+	}
+}
+
+#endif