diff --git a/js/main-editor.js b/js/main-editor.js
index a6d1a5e..ecf084a 100644
--- a/js/main-editor.js
+++ b/js/main-editor.js
@@ -826,6 +826,7 @@ export class Editor extends PrimaryView {
 
         // FIXME don't hardcode size here, convey this to renderer some other way
         this.renderer = new CanvasRenderer(this.conductor.tileset, 32);
+        this.renderer.perception = 2;
 
         // FIXME need this in load_level which is called even if we haven't been setup yet
         this.connections_g = mk_svg('g');
diff --git a/js/renderer-canvas.js b/js/renderer-canvas.js
index e0d3b56..315b5c8 100644
--- a/js/renderer-canvas.js
+++ b/js/renderer-canvas.js
@@ -26,6 +26,7 @@ export class CanvasRenderer {
         this.viewport_y = 0;
         this.viewport_dirty = false;
         this.use_rewind_effect = false;
+        this.perception = 0;  // 0 normal, 1 secret eye, 2 editor
     }
 
     set_level(level) {
@@ -205,7 +206,7 @@ export class CanvasRenderer {
     create_tile_type_canvas(name, tile = null) {
         let canvas = mk('canvas', {width: this.tileset.size_x, height: this.tileset.size_y});
         let ctx = canvas.getContext('2d');
-        this.tileset.draw_type(name, tile, 0, (tx, ty, mx = 0, my = 0, mw = 1, mh = mw, mdx = mx, mdy = my) =>
+        this.tileset.draw_type(name, tile, 0, this.perception, (tx, ty, mx = 0, my = 0, mw = 1, mh = mw, mdx = mx, mdy = my) =>
             this.blit(ctx, tx + mx, ty + my, mdx, mdy, mw, mh));
         return canvas;
     }
diff --git a/js/tileset.js b/js/tileset.js
index f91b888..a92f6e7 100644
--- a/js/tileset.js
+++ b/js/tileset.js
@@ -44,8 +44,13 @@ export const CC2_TILESET_LAYOUT = {
     key_blue: [5, 1],
     key_yellow: [6, 1],
     key_green: [7, 1],
-    dirt_block: [8, 1],
-    // xray
+    // FIXME these shouldn't be drawn with a hole when drawn in isolation, gruh
+    dirt_block: {
+        special: 'perception',
+        threshold: 2,
+        hidden: [8, 1],
+        revealed: [9, 1],
+    },
     ice: [10, 1],
     ice_se: [11, 1],
     ice_sw: [12, 1],
@@ -60,8 +65,19 @@ export const CC2_TILESET_LAYOUT = {
         wired_cross: [10, 26],
         is_wired_optional: true,
     },
-    wall_invisible: [0, 2],
-    wall_appearing: [0, 2],
+    // FIXME i think these are visible with the secret eye, but my tileset puts text on them, whoops
+    wall_invisible: {
+        special: 'perception',
+        threshold: 2,
+        hidden: [0, 2],
+        revealed: [9, 31],
+    },
+    wall_appearing: {
+        special: 'perception',
+        threshold: 2,
+        hidden: [0, 2],
+        revealed: [11, 31],
+    },
     wall: [1, 2],
     floor_letter: {
         special: 'letter',
@@ -92,8 +108,13 @@ export const CC2_TILESET_LAYOUT = {
         [8, 2],
         [9, 2],
     ],
-    ice_block: [10, 2],
-    // TODO ice block xray
+    // FIXME these shouldn't be drawn with a hole when drawn in isolation, gruh
+    ice_block: {
+        special: 'perception',
+        threshold: 2,
+        hidden: [10, 2],
+        revealed: [11, 2],
+    },
     score_1000: [12, 2],
     score_100: [13, 2],
     score_10: [14, 2],
@@ -128,7 +149,12 @@ export const CC2_TILESET_LAYOUT = {
     flame_jet_off: [8, 5],
     flame_jet_on: [[9, 5], [10, 5], [11, 5]],
     popdown_wall: [12, 5],
-    popdown_floor: [12, 5],
+    popdown_floor: {
+        special: 'perception',
+        threshold: 2,
+        hidden: [12, 5],
+        revealed: [13, 5],
+    },
     popdown_floor_visible: [13, 5],
     no_sign: [14, 5],
     directional_block: {
@@ -210,7 +236,13 @@ export const CC2_TILESET_LAYOUT = {
     ],
 
     fake_wall: [0, 10],
-    fake_floor: [0, 10],
+    // FIXME i think these are visible with the secret eye, but my tileset puts text on them, whoops
+    fake_floor: {
+        special: 'perception',
+        threshold: 2,
+        hidden: [0, 10],
+        revealed: [10, 31],
+    },
     // Thin walls are built piecemeal from these two tiles; the first is N/S,
     // the second is E/W
     thinwall_n: {
@@ -288,7 +320,12 @@ export const CC2_TILESET_LAYOUT = {
     blob: [0, 15],
     // FIXME blob animations span multiple tiles
     // TODO [0, 16] some kinda red/blue outline
-    floor_mimic: [0, 2],  // TODO [14, 16] with xray
+    floor_mimic: {
+        special: 'perception',
+        threshold: 1,
+        hidden: [0, 2],
+        revealed: [14, 16],
+    },
     // TODO [15, 16] some kinda yellow/black outline
 
     // timid teeth
@@ -792,7 +829,8 @@ export class Tileset {
     }
 
     draw(tile, tic, blit) {
-        this.draw_type(tile.type.name, tile, tic, blit);
+        // FIXME perception
+        this.draw_type(tile.type.name, tile, tic, 0, blit);
     }
 
     // Draw a "standard" drawspec, which is either:
@@ -947,7 +985,7 @@ export class Tileset {
 
     // Draws a tile type, given by name.  Passing in a tile is optional, but
     // without it you'll get defaults.
-    draw_type(name, tile, tic, blit) {
+    draw_type(name, tile, tic, perception, blit) {
         let drawspec = this.layout[name];
         if (! drawspec) {
             console.error(`Don't know how to draw tile type ${name}!`);
@@ -960,13 +998,13 @@ export class Tileset {
             // the overlay (either a type name or a regular draw spec).
             // TODO chance of infinite recursion here
             if (typeof drawspec.base === 'string') {
-                this.draw_type(drawspec.base, tile, tic, blit);
+                this.draw_type(drawspec.base, tile, tic, perception, blit);
             }
             else {
                 this._draw_standard(drawspec.base, tile, tic, blit);
             }
             if (typeof drawspec.overlay === 'string') {
-                this.draw_type(drawspec.overlay, tile, tic, blit);
+                this.draw_type(drawspec.overlay, tile, tic, perception, blit);
                 return;
             }
             else {
@@ -980,6 +1018,14 @@ export class Tileset {
                 this._draw_letter(drawspec, tile, tic, blit);
                 return;
             }
+            else if (drawspec.special === 'perception') {
+                if (perception >= drawspec.threshold) {
+                    drawspec = drawspec.revealed;
+                }
+                else {
+                    drawspec = drawspec.hidden;
+                }
+            }
             else if (drawspec.special === 'logic-gate') {
                 this._draw_logic_gate(drawspec, tile, tic, blit);
                 return;