diff --git a/Makefile b/Makefile
index 9c2c768..4862dc9 100644
--- a/Makefile
+++ b/Makefile
@@ -1,59 +1,72 @@
-SRC = universe-from-nothing
-BIBLIOGRAPHY = bibliography
+SRC ?= haskelltut
+
+ODIR ?= .
+
+BIBLIOGRAPHY ?= bibliography
 ALLSRC = $(shell find . -name "*.ms")
 
+SOELIM_OPTS ?=
+SOELIM = soelim $(SOELIM_OPTS)
+
+SPECHAR = specialchar2ms.sh
+
+PRECONV_OPTS ?= -e utf-8
+PRECONV = preconv $(PRECONV_OPTS)
+
+EQN_OPTS ?= -Tpdf
+EQN = eqn $(EQN_OPTS)
+
+# source-highlight stuff
+# GH_INTRO: instructions before each source code provided by source-highlight
+# GH_OUTRO: ------------ after  ---- ------ ---- -------- -- ----------------
+# GH_INTRO/GH_OUTRO: values are separated by ';'
+#
+GH_INTRO := .b1;.nr DI 0;.DS I;.fam C
+GH_OUTRO := .fam;.DE;.b2
+#
+export GH_INTRO
+export GH_OUTRO
+#
+# SHOPTS: cmd line parameter given to source-highlight
+SHOPTS = --outlang-def=./.source-highlight_groff-output-definition
+export SHOPTS
+
+# ghighlight brings `source-highlight` to troff
+GHIGHLIGHT_OPTS ?=
+GHIGHLIGHT = ghighlight $(GHIGHLIGHT_OPTS)
+
+GRAP_OPTS ?=
+GRAP = grap $(GRAP_OPTS)
+
+PIC_OPTS ?=
+PIC = pic $(PIC_OPTS)
+
 # -P      => move ponctuation after reference
 # -S      => label and bracket-label options
 # -e      => accumulate (use a reference section)
 # -p bib  => bibliography file
-REFER_OPTS = -PS -e -p $(BIBLIOGRAPHY)
+REFER_OPTS ?= -PS -e -p $(BIBLIOGRAPHY)
 REFER = refer $(REFER_OPTS)
 
 # -k     => iconv conversion (did it ever worked?)
 # -ms    => ms macro
 # -Tpdf  => output device is PDF
-GROFF_OPTS = -ms -t -Tpdf
+GROFF_OPTS ?= -ms -t -Tpdf
 GROFF = groff $(GROFF_OPTS)
 
-EQN_OPTS = -Tpdf
-EQN = eqn $(EQN_OPTS)
-
-PRECONV_OPTS = -e utf-8
-PRECONV = preconv $(PRECONV_OPTS)
-
-SPECHAR = specialchar2ms.sh
-
-# ghighlight brings `source-highlight` to troff
-GHIGHLIGHT_OPTS =
-GHIGHLIGHT = ghighlight $(GHIGHLIGHT_OPTS)
-
-VIEWER_OPTS = -
-VIEWER = zathura $(VIEWER_OPTS)
-
-SOELIM_OPTS =
-SOELIM = soelim $(SOELIM_OPTS)
-
-GRAP_OPTS =
-GRAP = grap $(GRAP_OPTS)
-
-PIC_OPTS =
-PIC = pic $(PIC_OPTS)
-
-# GH_INTRO: instructions before each source code provided by source-highlight
-# GH_OUTRO: ------------ after  ---- ------ ---- -------- -- ----------------
-# GH_INTRO/GH_OUTRO: values are separated by ';'
-
-GH_INTRO := .b1;.nr DI 0;.DS I;.fam C
-GH_OUTRO := .fam;.DE;.b2
-
-export GH_INTRO
-export GH_OUTRO
-
-# SHOPTS: cmd line parameter given to source-highlight
-SHOPTS = --outlang-def=./.source-highlight_groff-output-definition
-export SHOPTS
-
 $(SRC).pdf:
-	cat $(SRC).ms | $(SOELIM) | $(EQN) | $(GHIGHLIGHT) | $(GRAP) | $(PIC) | $(REFER) | $(PRECONV) | $(SPECHAR) | $(GROFF) > $@
+	cat $(SRC).ms |\
+		$(SOELIM) |\
+		$(SPECHAR) |\
+		$(PRECONV) |\
+		$(EQN) |\
+		$(GHIGHLIGHT) |\
+		$(GRAP) |\
+		$(PIC) |\
+		$(REFER) |\
+		$(GROFF) > $(ODIR)/$@
 
-include Makefile.custom
+# Keep options in memory for the recursive 'make' call
+export SOELIM_OPTS PRECONV_OPTS EQN_OPTS GHIGHLIGHT_OPTS GRAP_OPTS PIC_OPTS REFER_OPTS
+serve:
+	find . -name "*.ms" | entr gmake -B $(SRC).pdf
diff --git a/Makefile.custom b/Makefile.custom
index ca4116c..63deaa6 100644
--- a/Makefile.custom
+++ b/Makefile.custom
@@ -1,11 +1,11 @@
-RAM=/tmp
-# DOC: hstut rc
-DOC ?= universefromnothing
+SRC ?= universe-from-nothing
+ODIR ?= /tmp
+
+export ODIR SRC
+include Makefile
+
 upload:
 	scp $(RAM)/$(SRC).pdf tacos:/var/www/htdocs/t.karchnu.fr/doc/
 
-run_universefromnothing:
-	cat $(SRC).ms | $(SOELIM) | $(EQN) | $(GHIGHLIGHT) | $(GRAP) | $(PIC) | $(REFER) | $(PRECONV) | $(SPECHAR) | $(GROFF) > $(RAM)/$(SRC).pdf
-
-serve:
-	find . -name "*.ms" | entr gmake -B run_$(DOC)
+# VIEWER_OPTS = -
+# VIEWER = zathura $(VIEWER_OPTS)