diff --git a/Makefile b/Makefile
index 7c01f0e..05728b7 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,5 @@
-MMCFLAGS := -s asm_fast.par.gc.stseg
+# this seems to break day7 for some absolutely bizarre reason
+MMCFLAGS := # -s asm_fast.par.gc.stseg
 
 all: aoc
 
diff --git a/aoc.m b/aoc.m
index 8a9ffdc..cb7a7b4 100644
--- a/aoc.m
+++ b/aoc.m
@@ -23,11 +23,11 @@ main2(!IO) :-
    then
      read_lines_need(File, Lines, !IO),
      run_day(Day, Part, Lines, Out),
-     write_line(univ_value(Out), !IO)
+     output(Out, !IO)
    else
      die("expected day, part, filename")).
 
-:- pred run_day(int, part, lines, univ).
+:- pred run_day(int, part, lines, answer).
 :- mode run_day(in, in, in, out) is cc_multi.
 run_day(Day, Part, Lines, Out) :-
   if solution(Day, P) then
@@ -35,7 +35,7 @@ run_day(Day, Part, Lines, Out) :-
   else
     die("no solution for day %d", [i(Day)]).
 
-:- type sol == (pred(part, lines, univ)).
+:- type sol == (pred(part, lines, answer)).
 :- inst sol == (pred(in, in, out) is cc_multi).
 
 :- import_module day1.
@@ -47,6 +47,7 @@ run_day(Day, Part, Lines, Out) :-
 :- import_module day7.
 :- import_module day8.
 :- import_module day9.
+:- import_module day10.
 
 :- pred solution(int::in, sol::out(sol)) is semidet.
 solution(1, day1.run).
@@ -58,3 +59,4 @@ solution(6, day6.run).
 solution(7, day7.run).
 solution(8, day8.run).
 solution(9, day9.run).
+solution(10, day10.run).
diff --git a/basics.m b/basics.m
index d5adbc6..a2890d4 100644
--- a/basics.m
+++ b/basics.m
@@ -1,5 +1,6 @@
 :- module basics.
 :- interface.
+:- import_module io.
 
 :- type part ---> one; two.
 :- pred part(string, part).
@@ -8,8 +9,10 @@
 
 :- func part(part, T, T) = T.
 
+:- type answer ---> int(int); string(string); lines(list(string)).
+:- pred output(answer::in, io::di, io::uo) is det.
+
 
-:- import_module io.
 :- import_module list.
 :- import_module string.
 
@@ -52,6 +55,10 @@ part(one, X, _) = X.
 part(two, _, Y) = Y.
 
 
+output(int(I),    !IO) :- write_int(I, !IO), nl(!IO).
+output(string(S), !IO) :- write_string(S, !IO), nl(!IO).
+output(lines(Ss), !IO) :- write_list(Ss, "\n", write_string, !IO), nl(!IO).
+
 :- import_module exception.
 
 :- type die ---> death(string).
diff --git a/day1.m b/day1.m
index 851ea34..aa10a24 100644
--- a/day1.m
+++ b/day1.m
@@ -1,9 +1,8 @@
 :- module day1.
 :- interface.
 :- import_module basics.
-:- import_module univ.
 
-:- pred run(part::in, lines::in, univ::out) is cc_multi.
+:- pred run(part::in, lines::in, answer::out) is cc_multi.
 
 :- implementation.
 :- import_module list.
@@ -13,8 +12,8 @@
 :- import_module int.
 
 :- pragma no_determinism_warning(run/3).
-run(one, Lines, univ(det_head(go(Lines)))).
-run(two, Lines, univ(sum(take_upto(3, go(Lines))))).
+run(one, Lines, int(det_head(go(Lines)))).
+run(two, Lines, int(sum(take_upto(3, go(Lines))))).
 
 :- func go(lines) = list(int).
 go(Lines) =
diff --git a/day10.m b/day10.m
new file mode 100644
index 0000000..8cb5af6
--- /dev/null
+++ b/day10.m
@@ -0,0 +1,66 @@
+:- module day10.
+:- interface.
+:- import_module basics.
+
+:- pred run(part::in, lines::in, answer::out) is cc_multi.
+
+:- implementation.
+:- import_module int.
+:- import_module string.
+:- import_module list.
+:- import_module char.
+
+:- type instr ---> noop; addx(int).
+
+:- pred line(instr::out, list(string)::in, list(string)::out) is semidet.
+line(noop)    --> ["noop"].
+line(addx(N)) --> ["addx", X], {to_int(X, N)}.
+
+:- pred line(string::in, instr::out) is semidet.
+line(Str, I) :- line(I, words(Str), []).
+
+
+:- type reg == int.
+:- type cycle == int.
+:- type signal == int.
+
+:- pred regs(reg::in, list(instr)::in, list(reg)::out) is det.
+regs(_, [], []).
+regs(R, [noop | Is], [R | Ss]) :-
+  regs(R, Is, Ss).
+regs(R, [addx(N) | Is], [R, R | Ss]) :-
+  regs(R + N, Is, Ss).
+
+:- pred regs(lines::in, list(signal)::out) is semidet.
+regs(Lines, Signals) :-
+  map(line, Lines, Instrs),
+  regs(1, Instrs, Signals).
+
+:- func signals(cycle, list(reg)) = list(reg).
+signals(_, [])       = [].
+signals(C, [R | Rs]) = [C * R | signals(C + 1, Rs)].
+
+:- func signals(list(reg)) = list(reg).
+signals(Rs) = signals(1, Rs).
+
+
+:- func render1(cycle, list(reg)) = list(char).
+render1(_, []) = [].
+render1(C, [R | Rs]) = [X | Xs] :-
+  (if abs(R - C) =< 1 then X = '█' else X = ' '),
+  Xs = render1((C + 1) mod 40, Rs).
+
+:- func render(list(reg)) = lines.
+render(Rs) = map(from_char_list, chunk(render1(0, Rs), 40)).
+
+:- pragma no_determinism_warning(run/3).
+run(Part, Lines, Out) :-
+  if regs(Lines, Regs)
+  then
+    ( Part = one,
+        Indices = [20, 60, 100, 140, 180, 220],
+        Out = int(sum(map(det_index1(signals(Regs)), Indices)))
+    ; Part = two,
+        Out = lines(render(Regs))
+    )
+  else die("bad input").
diff --git a/day2.m b/day2.m
index 3a6dac3..a12016b 100644
--- a/day2.m
+++ b/day2.m
@@ -6,9 +6,8 @@
 :- interface.
 :- import_module basics.
 :- import_module list.
-:- import_module univ.
 
-:- pred run(part::in, list(string)::in, univ::out) is cc_multi.
+:- pred run(part::in, list(string)::in, answer::out) is cc_multi.
 
 :- implementation.
 :- import_module int.
@@ -97,5 +96,5 @@ run(Lines, P, F, Out) :-
     die("invalid input"). % lol
 
 :- pragma no_determinism_warning(run/3).
-run(one, Lines, univ(Out)) :- run(Lines, line1, score1, Out).
-run(two, Lines, univ(Out)) :- run(Lines, line2, score2, Out).
+run(one, Lines, int(Out)) :- run(Lines, line1, score1, Out).
+run(two, Lines, int(Out)) :- run(Lines, line2, score2, Out).
diff --git a/day3.m b/day3.m
index 77cd651..f2089d0 100644
--- a/day3.m
+++ b/day3.m
@@ -2,9 +2,8 @@
 :- interface.
 :- import_module basics.
 :- import_module list.
-:- import_module univ.
 
-:- pred run(part::in, list(string)::in, univ::out) is cc_multi.
+:- pred run(part::in, list(string)::in, answer::out) is cc_multi.
 
 :- implementation.
 :- import_module int.
@@ -60,9 +59,8 @@ go2(t(X, Y, Z), Prio) :-
     die("no item in common in:\n - %s\n - %s\n - %s", [s(X), s(Y), s(Z)]).
 
 
-run(one, Lines, univ(sum(Prios))) :-
-  map(go1, Lines, Prios).
-run(two, Lines, univ(sum(Prios))) :-
+run(one, Lines, int(sum(Prios))) :- map(go1, Lines, Prios).
+run(two, Lines, int(sum(Prios))) :-
   if threes(Lines, Groups) then
     map(go2, Groups, Prios)
   else
diff --git a/day4.m b/day4.m
index 97cc7a1..ef2e318 100644
--- a/day4.m
+++ b/day4.m
@@ -1,9 +1,8 @@
 :- module day4.
 :- interface.
 :- import_module basics.
-:- import_module univ.
 
-:- pred run(part::in, lines::in, univ::out) is cc_multi.
+:- pred run(part::in, lines::in, answer::out) is cc_multi.
 
 :- pred number(int::out, chars::in, chars::out) is semidet.
 
@@ -50,5 +49,5 @@ go(P, Lines, Out) :-
 
 
 :- pragma no_determinism_warning(run/3).
-run(one, Lines, univ(Out)) :- go(all_overlap, Lines, Out).
-run(two, Lines, univ(Out)) :- go(any_overlap, Lines, Out).
+run(one, Lines, int(Out)) :- go(all_overlap, Lines, Out).
+run(two, Lines, int(Out)) :- go(any_overlap, Lines, Out).
diff --git a/day5.m b/day5.m
index a8e0342..1b93090 100644
--- a/day5.m
+++ b/day5.m
@@ -1,9 +1,8 @@
 :- module day5.
 :- interface.
 :- import_module basics.
-:- import_module univ.
 
-:- pred run(part::in, lines::in, univ::out) is cc_multi.
+:- pred run(part::in, lines::in, answer::out) is cc_multi.
 
 :- implementation.
 :- import_module int.
@@ -96,7 +95,7 @@ interp(Part, {Count, From, To}) -->
   take_n(From, Count, Res), put_n(Part, To, Res).
 
 :- pragma no_determinism_warning(run/3).
-run(Part, Lines, univ(Out)) :-
+run(Part, Lines, string(Out)) :-
   if input(Towers, Insts, Lines, []) then
     foldl(interp(Part), Insts, Towers, Res),
     from_char_list(map(det_head, Res), Out)
diff --git a/day6.m b/day6.m
index ee8f8b5..8fe8bcc 100644
--- a/day6.m
+++ b/day6.m
@@ -1,9 +1,8 @@
 :- module day6.
 :- interface.
 :- import_module basics.
-:- import_module univ.
 
-:- pred run(part::in, lines::in, univ::out) is cc_multi.
+:- pred run(part::in, lines::in, answer::out) is cc_multi.
 
 :- implementation.
 :- import_module int.
@@ -26,7 +25,7 @@ length(one) = 4.
 length(two) = 14.
 
 :- pragma no_determinism_warning(run/3).
-run(Part, Lines, univ(Out)) :-
+run(Part, Lines, int(Out)) :-
   if Lines = [Line] then
     Len = length(Part),
     (if start_index(Len, to_char_list(Line), Out0)
diff --git a/day7.m b/day7.m
index ab36eb8..17d5d2b 100644
--- a/day7.m
+++ b/day7.m
@@ -1,9 +1,8 @@
 :- module day7.
 :- interface.
 :- import_module basics.
-:- import_module univ.
 
-:- pred run(part::in, lines::in, univ::out) is cc_multi.
+:- pred run(part::in, lines::in, answer::out) is cc_multi.
 
 :- implementation.
 :- import_module int.
@@ -53,5 +52,5 @@ go(one, Top, sum(map(size, Found))) :-
 go(two, Top, det_head(sort(map(size, Found)))) :-
   find(size_gte(size(Top) - 40_000_000), Top, Found).
 
-run(Part, Lines, univ(Out)) :-
+run(Part, Lines, int(Out)) :-
   if dir(Top, Lines, []) then go(Part, Top, Out) else die("bad input").
diff --git a/day8.m b/day8.m
index cdf3205..fdbbf00 100644
--- a/day8.m
+++ b/day8.m
@@ -1,9 +1,8 @@
 :- module day8.
 :- interface.
 :- import_module basics.
-:- import_module univ.
 
-:- pred run(part::in, lines::in, univ::out) is cc_multi.
+:- pred run(part::in, lines::in, answer::out) is cc_multi.
 
 :- implementation.
 
diff --git a/day9.m b/day9.m
index b570e9b..dbc5428 100644
--- a/day9.m
+++ b/day9.m
@@ -1,9 +1,8 @@
 :- module day9.
 :- interface.
 :- import_module basics.
-:- import_module univ.
 
-:- pred run(part::in, lines::in, univ::out) is cc_multi.
+:- pred run(part::in, lines::in, answer::out) is cc_multi.
 
 :- implementation.
 :- import_module int.
@@ -95,7 +94,7 @@ run0(Part, Lines, Out) :-
   foldl2(next, condense(Dirs), Start, _, init, End),
   count(End, Out).
 
-run(Part, Lines, univ(Out)) :-
+run(Part, Lines, int(Out)) :-
   disable_warning [no_solution_disjunct] (
     not run0(Part, Lines, Out) => die("bad input")
   ).